In a shorter version. Airdrops are not profitable, in most situations all drops prove to be a scam and bring no profit. Now nobody want give you money for free so you have very small chance to get anything
I saw an airdrops that cost 1500$ (and I'm serious), so not all airdrops are scam. Unfortunately the rate vali/scam is something about 1/100 nowdays.
Airdrop is not free money. You are payed for fulfilling tasks. ICOs need to have good social accounts with lots of followers. So they go the easiest way to get followers - pay them. As always good projects don't need it, but scam or near scam ICOs can't do without it.