I think that airdrop now are give you little profit, because most of airdrops are scam, they give you reward in few amount of token and worth nothing in $, for now i prefer not join any airdrops because i get nothing if i join now, everyday people can make thousand airdrops and the tendency of scam project will be 90%.
You estimate about 90% of the project is scam, so about 10% can make a profit. That's enough for many crazy newbies because of it, although the value of these coins is very low.