Same reason you can't just go out and buy a car with your own damn money and legally drive it without a license. It's in the public interest that certain groups

Same reason you can't just go out and buy a car with your own damn money and legally drive it without a license. It's in the public interest that certain groups meet certain requirements in order to perform certain tasks. There's plenty of problems that come out of this, but generally people who support it think it's better than no regulation at all.