A lot of C-level pay is to tied to the company's earnings-per-share. A buyback makes that number go up without actually improving anything. It's a lazy way of getting your bonus. Here in the UK it was illegal for a very long time.
If this is a lazy way for a CEO to meet goals, I'm as concerned how lazy the board is in not putting scenario exceptions in the bonus to allow for stock concentration via buyback. It would be a fairly simple line in a bonus plan. Likewise they shouldn't be punished if share are diluted via raising money on the markets if that is the best things to do at the time.
