Even if the airdrops are scams you won't lose your money because participating is free, so what's the legal justification for the ban?
I disagree with SEC action towards airdrop. But as i stated above, some airdrop makes you do certain task which takes some time. So while you don't lose money, you lose your time. There's also risk of your email address or other personal data sold by them.
Well airdrops typically has some task to accomplish to get rewarded, airdrops without tasks are not common on the crypto space, i hardly noticed any airdrops campaign without carrying out certain tasks.
Again, air drops campaign that requires KYC is unnecessary and SEC should know that airdrops are free rewards for doing very little tasks like just retweeting a posts on Twitter and other social networks out there.