I have long hair and a beard and mustache. Plenty of reasons why a trans person might. For me, it's a combination of hiding I'm trans, laziness, sensitive skin that makes shaving more annoying, and not having time for laser during the summer because work.

But some people like that kind of gender fuckery.

Otoh, a lot of transphobes imagine trans women as just guys wearing women's clothes, so they probably don't get the nuance to even consider why a transfem person would have a beard or get how fear of violence against all trans people could potentially motivate someone to act in self defense like this...