Well, you're not wrong, but you're not correct also.
Airdrops are mainly used nowadays to fill the telegram channels with fake people, so that the project looks more interesting than it actually is.
I know alot of airdrop providers, and basically that's just it. They get people who immediately mute the group.
So is it a good marketing tool? Fuck no, it's not.
Could those funds be used better? Yeah
If they feel or have time to spend then surely they can bring some small tasks or any thing relate to this for giving their tokens because in airdrops they have no real users.