airdrops do have there uses.. unfortunately scammers have taken advantage of it and given airdrops a bad name
if a legitimate project doesn't want to deal with legal issues right away an ICO might not be best.. by airdropping there coins they can avoid legal issues in most countries.... also by the team keeping some of the coins it makes them work for their money.. some of the bigger successes will come from airdrops.. you will see this soon...
but with good there is also bad... a lot of airdrops are being used as a marketing tool to get people to buy more.. and where you buy more the team dumps all their coins then disappears... thats when you need to use your judgement on which airdrops are good and bad.. but just because a coin was airdropped doesn't mean its bad.. if the project is solid and continuing to move forward.. then it might be the best free coin you got via airdrop