4) That dirty back-room deals are usually done by lobbyists. In reality, a company that wants to pay off a politician will just donate the money, or offer a lucrative job. Lobbyists are under a lot of scrutiny, so they are the worst people to handle bribes.

If you're a regular citizen / company, you can pay a politician $10,000 to have dinner with them, and hire their best friend as a consultant. If you're a lobbyist, you can't buy them a coffee.