It is true that bounties usually pay off better than airdrops, so it is good to try to rank up and join bounties.
But there are also some exceptions. For example Byteball and DeepOnion were (and still are) distributed via airdrop and the early participants probably earned very good money from that. You just have to do some research if the project is worth your time... but it's quite difficult, because even doing the research takes a lot of time