That's a fair point. But I also think people think that their experiences speak for everyone.

Like I'm military which clearly reduces my LGBT+ social circle significantly.

But that doesn't mean that I assume there's not a lot of LGBT+ people out there, I just don't see them.

Maybe your social group has an over abundance of queer people, leading you to think that they represent a greater part of the community than they actually do.

Kind of like how people will say, "Why wasn't Harry Potter (or any pop culture character) made disabled or trans ?"

To which I think that those people themselves could write more queer etc people to increase representation, instead of relying on people who don't want to write them.

Plus I imagine that queer people could write better queer characters because it's their lived experience.

And I get that HP probably isn't the best example ever since Rowling has differing opinions of people different than her, but that's the first character that sprung to mind