not all airdrop ends scam, there is still airdrop that pay, even some people have got big result from airdrop, i've read this on some threads, some get lot result from airdrop.
But those are the exception rather than the rule most airdrops will end in failure after all why they are giving away their coins for free? A bounty campaign is not giving coins for free they are exchanging a small amount of their coins to gain promotion in the forum and other social media websites so if I were you I will not expect any kind of positive results from airdrops.