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%.
I do not think the rate of scams in airdrops are that high, what happens is that the developers of those coins did not realized how much work it will take to develop a cryptocurrency and eventually when they see their efforts are not getting them where they want they decide to abandon the project and the coins never get distributed or do not have any value.