Airdrops are marketing strategy of startup companies that runs ICO to reach more visibility with very low/zero cost of money.
Since any developers can create tokens on ethereum blockchain for free, we have to be very careful when deciding to enter the airdrop programs. Most of them are bad, but few some are legit and good. It's all back to our capability to research the background (fundamental) of airdropped tokens.
No,
airdrops are what you do with.
My airdrop is not marketing but a way to allow people to entre for free in my site profit.
The ethereum blockchain is a way to go out for ETH and a way to go in for WSPU2.
I have so far never need the ERC20 token system to run my sites,but the ERC20 token is really an opportunity to improve it.
So please do not be so paranoiac and do not see scammers every where who want rob your money.