they do little task like follow a twitter page or like a Facebook they mostly dont get the reward
that is not "airdrop" that is a "payment" for a job that they do. the job is small and meaningless (an advertisement of sorts) but it still is a job and they are getting paid for doing it so you can't call it an "airdrop".
This. And also, you're pretty much paying them with your data. Most if not all airdrops require your email, mobile number, and personal information to submitted(though you can fake your personal info), and some even going as far as requiring KYC, which is significantly more dangerous.
If airdroppers think their personal information is worth a few cents(or sometimes worth zero) of shitcoins, then ok.