Amundies
Commander-in-Chief
Doesn't mean you can just start up shop and expect the money to come. Companies go to firms like UBS, JPM, etc. because of the reputation that they have built up over decades (centuries even, for some). That's something you don't get if you create your own company. If working for a large firm, in return for getting less of the profits you generate yourself you're getting guaranteed work. If you work for yourself, you get all the profits for yourself but getting work is no longer definite.The chances of that are a fraction above zero.
In regards to "being rich", you are not going to make big amounts working for someone. Not saying working for someone is a bad thing, but as long as you are an employee, you can't earn nearly as much as the business owner.
It is estimated that the employer will generate 4 times the amount income of your earnings. So if you salary is 100K, the business will earn 400K from your work. (Keep in mind that not all of it is profit but a lot of it will be.)
In the end, the economy is business driven and when you are an employee you are just a cog for the company you work for to generate lots of profit.
Also you said "you can't earn nearly as much as the business owner". That's what shares are for So if you work for a company, and own shares, you not only get definite work (and salary) but you also own parts of businesses which earns you more money.