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.
Airdrop as ruled does not work well at attracting investors. I think it will be useful only to increase the activity on social networks and increase traffic to the project site. In terms of attracting investment it is better to use other tools.