The main problem of kyc in bounty is the team says about kyc after all work done. It is really cheating. I never go through a campaign which asks kyc.
That's a problem especially if you participated for 3-4 months. In this case you have two ways: pass the KYC or just leave campaign without any tokens.
Managers and the company insure themselves by pointing out that the rules may change any time. So if at the beginning there was no KYC it may appear at the end.
Honestly, in most cases it can be absurd and I think sometimes the team just basically uses it to cheat the bounty hunters just as OP mentioned. How can someone participate in your project for months as a bounty hunter and then all of a sudden you just change the rules after the ICO about some KYC you never mentioned before? It is really uncalled for.
For instance, I as well as some other people participated in a GoldMa bounty campaign and immediately the ICO ended, there we get to see the rules for a compulsory KYC, I really see that as high level of dishonesty on the part of the team and a way to just use and dump most of the bounty hunters who may not want to go through KYC.