There's more to it than that. Board members of large corporations tend to be CEOs of other large corporations. Not only do they see each other at charity events and such, they have a vested interest in not being too hard-nosed about compensation.
The question is why the shareholders put up with it, and I don't have an answer to that question.
Because it sounds like the safe, experienced play. It does work for a lot of companies (says something about the companies more than the CEO), and I would suppose it is easier to make deals to keep the company going when you have all the "club" contacts. When it fails, it fails in amazing spectacular ways.
I guess many should be sorta happy since it allows untried upstarts to disrupt the market and truly well run companies to expand. I feel sorry for all the people caught up in the fail.
The question is why the shareholders put up with it, and I don't have an answer to that question.