The time to complete an airdrop is very short. I don't think this is a waste of time because some airdrops still allow us to get a small amount of revenue. On the contrary, some bounty tasks that will take weeks or months to complete will eventually disappear. This is the most time-wasting thing!
something is in your words true, but it is reliable only if you are picky with the air drops that you complete, if you will perform every each it would be definitely a great wastage of time.