Working for yourself means that you are not accountable to anyone else, meaning that you are in charge of your own business. In this case, you can be considered solely self-employed and you do not have to answer to your boss for your work. Working for yourself means a lot of freedom and you are the owner of your own company. It can basically be thought of as an entrepreneur or business where you are in charge of your entire company and have employees under you. You are your own boss.
It's true however, the freedom part is only true to certain extent.
Yes we have the freedom to be working or not, depend on our mood since it's our business but if we truly living off the business and the business is still on its early stage and developing, it's gonna be a tough time to have freedom at that time.
My first hand experience is that starting a business, working for ourselves will cause us to work much more often and have less leisurely time than being employed.
However, the big difference is that we're trying to achieve our dream, not paid to do something for other people.
Early stage and developing doesn't make sense been a taxi driver like one of the examples that OP used, what is developing have to do with driving people from one location to another and getting paid?
Some businesses are just rendering services to people and getting paid in return, there is no development attached, some jobs don't even need skills like software engineering, just learn how to drive and start doing it to make money, the end.
Alsmost everyone knows how to drive but many don't have the time or a car, but to get to their work places they need a taxi, freedom for example comes with choices we make.
For some, they choose freedom only when millions are already made, breathing in the bank or other businesses, while some dome even bother, they think more about death than been alive, they work base on their own effort or energy on that day, how much they make or must make doesn't worry them.