It may shock you to learn that some of us actually, legitimately do care about being inclusive of others in a multitude of ways. It costs nothing to be kind and sharing/respecting another person's pronouns takes no more effort than any other way you might refer to someone. That a few people get tilted over something that does exactly zero harm to them is inconsequential because, like I said, there's no harm.

And you can just use their name and skip over them in an email signature, anyway.