1) Some ICO's don't want to do it
Isn't it obvious that if the team do not allowed their tokens to be escrowed, then maybe it is a potential scam in the end. Also, it is possible that you and your bounty hunters will not get paid by the end of the ICO.
2) Some ICO's can't do it as the tokens will be released on TGE
Is it hard to find those types of ICO's who's tokens can be released before Token Generation EVent?
3) There's hardly any trustworthy escrow services out there
Are you not able to escrow it yourself? There are some BM's who can do that. It's just a way to protect yourself. Anyways it's just a suggestion