We usually think about free is totally free like just an airdrop. But actually, all of those things are not totally free. It is only a reward for completing a simple task. I don't think it is really encouraging but for those who did nothing, why not try?
I could say that this is a good way to start earning in crypto for newcomers but just to remind them also that be sure that they are visiting the right/legit site otherwise, they are just wasting their time. And aside from that, we must not expect huge rewards.
to expect big rewards we can collect prizes then we can invest in potential coins, I have been doing this for a long time. but I'm looking not from airdrops, but from signature campaigns. It would be a shame if we didn't try it, even though currently the prizes are not as big as in 2017, there's no harm in trying to get a little prize, which of course can be useful, as well as expanding knowledge about cryptocurrency. Even though sometimes I don't get a prize, I still faithfully participate to try my luck
A better approach would be to simply keep the Bitcoins that you get from a signature campaign and not sell them until the market enters the bull run and Bitcoin and all cryptocurrencies start going up because signature campaigns pay their participants with Bitcoin. But I guess that works only for those who wish to invest their earnings only in Bitcoin and not altcoins because altcoins carry a lot of risks apart from a few of them like ETH and LTC, etc.
One more thing that might be a hurdle for someone doing this is the need for money. People that use signature campaigns earnings only as savings or personal money can easily save that up so that they can sell them for a higher price in the future, but those who might not be earning enough with their day jobs, they might have to sell them and use the money for their personal expenses.