Nowadays most of the airdrops are scams.But there was some good ones also.But we can't get a good idea about airdrop untill we receive.If we receive airdrops some of them are also scams.But If you try hard you can earn some BTC or ETH from airdrops.
This is true, I wouldn't even waste my time looking for airdrops, if you are not living in the US/China you can make some money on bounty campaigns, other than that there is nothing useful