Obviously, it is not easy to hand out your identity for something that might not even have value. Security reason is not the only reason why bounty hunters run away. KYC should not be compulsory for bounty hunters as they only help to spread the word about the project, some bounty managers also use kyc to curb multiple account usage too, but KYC is really a high risk.
Most hunters avoid KYC because worry on ID safety. Like or not, KYC will be a standard in cryptocurrency space and its needed to comply government regulation. But in others side, crypto is about the freedom to hide our identity and this is should apply in ICOs. But mostly, bounty that require KYC is more legit.