Airdrop is a lure for the people to grab the free token and expecting a nice outcome to bring free money to them, as a bait for the people for the project to have a better number of audience and group members, airdrops are required to join their telegram group, facebook, and twitter.
Some of the airdrops are waste of time as some of these are just scam trying to give free tokens but the real point is they are to hold a large amount of token and make a pump and dump in the market.