Two reasons.

1: Many of them are too embarrassed to come out and say they were taken in.

2: They probably intend to take advantage of the system to make their money back and get back at those who "screwed" them. They didn't seem to realise there really is no honor among thieves, until it was too late. Once all the little fish are gone, sharks will start to eat each other. Of course they lost a lot of money, but most did not lose all of it, so they just start over. How many times has Trump filed bankruptcy only to end up back at the top?

They don't want the regulation because if the recovery plans work there will be more small fish to eat so they can rebuild their bank accounts easier.