Airdrop is not very popular, but he is very much advertises the project. Many new users visits the social network of the project and share it on your pages, I think this is a great solution for your project.
I agree with you that airdrop can be useful for a project and if it is properly organized, you can reach a large audience and disseminate information about the project. Due to this, the project receives new investors, increasing awareness and growing community.