Yes it's only small rewards but if it were much bigger rewards it wouldn't be good for the projects as there would be better marketing alternatives. Also don't forget that it's so easy to sign up to airdrops that you really shouldn't receive that much.
I really do not see any point in airdrops but really though, who cares since it is free money anyway and you would not really have to do much most of the time. The thing with airdrop is that you will have to be ready to hold as long as you want to.
Some may end up doing great in the long run and some may not, but the idea is to have a huge community behind the coin. It is easy for a project to end up highly volatile in the long run, when very few people are holding the market.
Airdrop is used for promotional purposes so if it's successful, then it would be beneficial for both the participant and project creators. Airdrops generate advertisement for the project and there are times when you would have to accomplish some promotional tasks such as making a retweeting or sharing on facebook to participate in an airdrop.
Not in all cases that airdrops are profitable when you hold. There are times when it's more profitable to sell after the token release because the price then plummets down after dumps have been made. Airdrops are not always made for long term but its pretty easy and
free money for the participant and
free cost for the developers.