Just because you're joining in the application for one code path doesn't mean all of the code paths are doing the same thing. There are certainly valid use-case

Just because you're joining in the application for one code path doesn't mean all of the code paths are doing the same thing. There are certainly valid use-cases for joining in the application because application layer can often times be horizontally scaled more cheaply/easily than the persistence layer. So in a scenario where you have plenty of network IO being under utilized for your database, it's not unimaginable where joining in the application layer would be preferable.