I think tha most textbooks don't include
LGBT thins because it is such a large topic of discussion and a lot of people fight about it.
Granted, people also have opinions on the other things listed though it's not as large of an agrument.
In my Geography text book, it featured a gay man going to Mardi Gras and everyone in my class was mature about it.
I guess they don't want to offend any
LGBT people or cause argument.