There are tons of airdrop you can join and earn free coins in their promotional activity by participating and completing the task. There are some that after holding for some time it reach high market value just being stored a lot of those coins in which others think that are not useful. However, I see a wallet that reaches total of 200$ with just those combine coins in the wallet having 2$-10$ value of the variety coins.
There are fewer airdrops now because of Ethereum very high fee, some of them are shifting to Binance smart chain, some airdrop now cannot be considered a true airdrop they obliged you to complete some tasks like what bounty hunters are doing, so many airdrops are useless like those who ask for KYC, they just do this to collect your vital information and sell it in underground.