I think the problem lands somewhere between “widespread corruption” and “never.”
Salespeople can hit their quotas without kickbacks.
What I do see from time to time is this happening “fully disclosed”’at the very senior level. A CEO of a major database company convinces the board to buy a firm that he has an interest in. A CEO “allows” a company to rent out his property for corporate housing. These are fully disclosed, and therefore considered acceptable.