Even if the admins wanted to they couldn't do it due to the very nature of anonymous imageboards and forums. Anyone can pretend to be anything and you can't easily detect who's a tranny and who's not (especially if there were to be a ban in place, which would make the trannies keep their troonery a secret).
At that point, it becomes a slippery slope where the janny decides to ban everything xhe doesn't like because xhe thinks everyone who posts said thing is a tranny even if that isn't the case. It's a concept that's so easily exploitable that it probably cant even be laid out to begin with.
And besides, there's barely any actual trannies in the soysphere as opposed to just regular queers. I used to post this one video detailing how the pride movement was founded by pedophiles on the sharty and the jarty around the time of the soypoclypse and I was legit receiving angry responses and people trying to argue.