Assuming this is a serious question it is because working for yourself is not that easy. It requires sales and marketing to get your value out there to the people that are willing to pay for it.

Working for someone else is easy because there is an established system to connect you to the people that are willing to pay for your value. That channel doesn't exist for everyone, especially people with skills in areas that do not commonly hire contractors, like IT.

Because value is a combination of human labor AND the means of production and the means of production aren't owned by working people. I can start making cheeseburgers but McDonald's owns the efficient equipment, the marketing, the good locations to sell them, etc. such that I can't possibly make profit outside their system. So I'm forced to essentially rent space in their kitchen in order to be compensated.