Merging that PR can take a lot of time for testing, and also risks locking in some feature into the project, which the maintainer does not need or use, but they're now stuck supporting (owning) from here on.

Typical conversation:

- contributor: I need feature X for my big client, it's super important, please support it.

- maintainer: interesting, I'm not familiar, but I'll take a few hours to review. Can you help maintaining it? write tests? help fix other bugs?

- contributor: no. corporate does not allow me to. I am too busy, have other paid projects to work on, why would I do things for free?

Don't get me wrong, everything I do is FOSS, but it's easy to be brunt as a maintainer.