Because in a democracy, it is always easier for one bad actor to spend $xyz,000 on lobbying the government to let them steal $10,000,000 from the public, then for 300 million people to organize, and lobby against you stealing 3 cents from each of them. It's an obvious defect of the system.

Of course, in 2019, half of those people have been convinced that they'll become rich, if they just let large firms fleece them.