I would generally agree with you that KYC is not necessary for an airdrop, especially since I work for a project that has conducted airdrops without KYC already. It's likely that projects that try to conduct KYC for airdrops have either been told they have to do this under the law, or they want to ensure they can contact you later for marketing. Either way, it leaves a bad taste in a user's mouth, and they should avoid conducting KYC for airdrops if they can.