You forgot about KYC! First you get the tantalizing airdrop promo. All this free crypto, just do some tasks. Then months later, boom, you need to do arduous KYC for what turns out to be $5 worth of shitcoin. So if it was 2017 or earlier, I would agree with you that airdrops are a fun and easy way to get some free crypto that you can turn into BTC. But in 2018 forget about it. KYC is for the birds.