You have to be very careful when sending your identity documents, not all of them are real projects, some are scams wanting to get your personal information so they can abuse it later on. Cibus for example collected my identification, gas also and yet never sent me any tokens
KYC verification can be important for large investors. I think it's useless to run KYC in airdrop or bounty. Participants get so little rewards that their influence on the market is none. It's not known who has personal data and where it's stored and whether it's well protected against leak.