because people change their pronouns and they get pissed off if you use the wrong one.
I’ve had trans people tell me their pronoun. OK, cool. Then a few weeks/months later, they change it. Then they jump down my throat for not knowing the new one they have picked.
Look, most trans people are cool, but there are a few out there who are DETERMINED to be complete assholes about it, no matter how hard you try.