Obvisouly for the free tokens, but other than that, what else incentivise you taking the time to do the airdrops? Most of the time, I found that the airdrops often give little to no return. I just started to get into the crypto thingy. I feel like it is better off finding those ICO projects and considering investing in rather than chasing like 5 dollars?
I have been part of a couple airdrops before and there are couple of reasons to join into something like that.
First of all if you have done something to earn a right to join the airdrop instead of just one of those airdrops where everyone gets some than you definitely deserved to be paid, that is a big reason, some airdrops require you to do something and even if its just following on twitter or some silly stuff like that or not than you still deserve it (twitter was a bad example I think since they can't really check to give out airdrops) however if it requires nothing than simply you can just both show your support to the project and get paid at the same time, you don't have to sell it right away and more than likely you can't sell right away but you can keep it for future profits, there is one coin I still keep and not sold and it has increased over 100% since I got in.