Airdrop is a good idea to attract attention to the project and unite the community.
Also airdrop allows people to earn money. That is why airdrops popular now.
Promotion is important for every project and airdrop is a way of promotion.
Airdrops always attracts attention because they allow people to get free tokens. But the most important is to create a project that is really necessary for people that tokens of the project will be in demand in the future.