do you know why people use it? Because I never understood it
It exists to include all the other groups that are “like transgender, but different”, ie, nonbinary people and whatnot. In theory this is a good idea. The problem is, it often gets used to say things like “trans* men” and “trans* women”, which is basically saying, “yeah there’s this group BUT PLEASE GIVE ATTENTION TO THESE OTHER GROUPS TOO”. It’s criticized by a lot of trans women because, well, the whole “including everyone else” thing is kind of what caused trans people to be lumped in with gays/lesbians/bisexuals (which, by the way, you can be IN ADDITION to being trans), ending up at the end of the acronym. It’s especially frustrated when you remember that the whole “gay rights movement” started primarily with trans women of color at the Stonewall Riots, not white gay men.
so, tl;dr: inclusion is good, but we don’t exactly have the best history of it working out for us…