But why?

The Rubik’s Cube was a toy unlike any that the world had seen. It wasn’t a doll. It wasn’t a truck. It was a cube. And, its sole function was as an enigma to be solved.

Cube inventor Erno Rubik has theorized that his puzzle’s success is based on the “basic desire to create order out of chaos” or due to its embodiment of “our most basic contradictions: simplicity and complexity, dynamism and stability, pleasure and frustration…”

I posit that the Rubik’s Cube is the Venus Flytrap of puzzles. It lures you in with bright colors and a simple objective, only to leave you helplessly lost.

First-time cubers see a simple challenge, and ask themselves, “What’s all the fuss? How hard can it be?” And they just have to try it. And try again.
source:https://www.crowdspring.com/blog/successful-product-design/

wonderopolis.org › wonder › who-invented-sticky-notes

The termination of their partnership enraged President of Sony .In order to compete against Nintendo, he asked Ken Kutaragi(the creator of “PlayStation”) to develop the PlayStation Project. Soon after demonstrating their hardware in 1994, many game publishers began to approach Sony, notably Electronic Arts and Namco. 

Source:
https://www.smh.com.au/technology/your-turn-a-brief-history-of-sony-and-the-playstation-20131023-2vyql.html

Colgate-Palmolive and Altitude determined that the keys to reconnecting with users were differentiation from competitors, superior performance, and outstanding ergonomics. Focused on human centered design, Altitude developed the product with refined features and performance, delivered on their needs.

https://www.altitudeinc.com/casestudy/colgate/

When patients were going into the operation, they were really nervous and afraid. So the first thing that almost every nurse did was hold the patient’s hand to comfort them—an obvious human element their client hadn’t noticed.  
IDEO went back to their office to brainstorm potential solutions, and they came up with a device that had a thumb scroll so nurses could do everything with one hand. That way they could input data and hold the patient’s hand.

2. Designing a toothbrush for kids : 
In 1996, Oral-B asked IDEO to design a new toothbrush for kids. And the first thing the IDEO team said was that they needed to watch kids brush their teeth.

As you can probably imagine, the Oral-B executives thought this was a strange request. You want to go into people’s homes—into their bathrooms—and watch their kids brush their teeth? Everyone already knows how people brush their teeth, is that really necessary?

As strange as it sounds, that’s exactly what they did. They needed to see how kids actually brush their teeth, and they didn’t want to make any assumptions.

During their observations, they noticed that the way kids hold their toothbrushes is totally different than adults.
Since adults have manual dexterity in their hands, they tend to use their fingers to manipulate the toothbrush with very fine movements. But kids just grab the toothbrush in their fist.

The problem with adult toothbrushes was that they were hard for kids to hold. Since they were so small, they just flopped around in the kids’ hands and were difficult to use.

That one simple observation led to a new style of toothbrush: the squish gripper.

And it totally innovated the kids-toothbrush space.
If you go into any supermarket or corner store today, you’ll notice kids’ toothbrushes have fat, squishy handles. That’s the power of observing the behavior of your users and integrating it into your design process.

So i think coming up with a company that can cater to the needs of end users using HCD is itself a very big product to the field. 

Reference  : https://www.usertesting.com/blog/how-ideo-uses-customer-insights-to-design-innovative-products-users-love

The company was founded as a result of what Jeff Bezos in 1994 in garage of his rented home. At 30 years old, he began to see the internet revolution take place, and made the decision to quit his job and start an internet company. 

The company started of with the selling of the books. Bezos wanted books to be accessible to every reader, no matter where they lived. He wanted Amazon to be the go-to resource for people everywhere to purchase books. So, in July 1995, Amazon opened its doors as one of the first online bookstores and slowly with time they realised that the people were looking for everything they would want in a single place so they formed a team who would go and ask the people of their locality if they would buy their daily essentials online sitting at home and they got a positive response so through their company they could make that happen. So then they decided that they need to expand thier company and start off with selling other stuff along with the books.

Within two months, Amazon’s sales were up to $20,000/week. However, the company has continued to plow their revenue back into growth and then slowly climbed its way to the top of the online market.

All the age group people are happy with the products and their quality , as they experienced the results from the results after using them.

SOURCE
Its a journal: https://journals.sagepub.com/doi/pdf/10.1177/2278533718800860

Fitbit realized that "share all my stuff with everyone" wasn't the best default option, and it changed its site so that user information would be private by default. Stand-alone fitness trackers were iPods in a world moving to iPhones.

One of the problems of being an innovator is that you can end up at the forefront of issues you might not have considered, and in the case of Fitbit one of those issues is privacy.

Health data recorded by Fitbit isn't legally protected in the way normal medical records are, and that means Fitbit's data can be subpoenaed by the relevant authorities.

 “All my inventions have begun with the identification of a problem that needs solving.”- Said Ms. Haberman.   
In the beginning, selling the Anywayup cup through major points of sale, such as supermarkets, was difficult due to their reluctance in dealing with a one-product company. This, however, did not stop Ms. Haberman and her team from using their creativity to convince the chief buyer of a major British supermarket chain to take a chance.The team decided to show the buyer the product’s ingenuity by sending her an Anywayup cup filled with blackcurrant juice and a note stating, “If this reaches you without spilling, give us a call!” It did not spill. The product reached store shelves within a few weeks and sales began to soar. In later models of the Anywayup Cup, the plastic was made semi transparent to reveal the liquid level. 
Referred links :
1) A Book called
"1001 Inventions That Changed The World Since 26,00,000 BCE"

2)https://www.wipo.int/ipadvantage/en/details.jsp?id=903
3)https://habermanbaby.com/suckle-feeder/browse-by-brand/anywayup

As the sky was filled up with gray smoke, the rays of Sun didn’t reach the ground. A small ice age started. Temperature decreased. Food got over. No crop could be planted without the Sun.

So, people started eating animals. Cats, Dogs etc. Then came the turn of the Horses. After Horses got finished in Britain, they had no way of transportation. Year was 1816, so no other mode of transportation was there.
so for the need of people transportation Karl Drais  thought of a device so that instead of walking for hours they can cover more distance by riding. 
So he invented a Velocipede (which later became a Bicycle).  initially it didn't have pedals they used to move it with their legs later on it got improved.