> As for pronouns, in most languages, you can know the [grammatically] correct gender automatically from the name.

But what if you can’t? Or there aren’t enough context clues to determine this? For example, my username contains my name in it; do you have any idea what my gender is? Or what I’d I had a “gendered” name but actually had a different identity personally?

But really the problem is that gender comes up in conversation a lot more than orientation. You can get a lot further in a conversation without the latter than the former, so some people see it fit to frontload that information.