Except that the assumption of cis as a default is a function of cissexism.

(I don't mean to get all transfeminist in yr face, I just think we as consumes have a lot of power in how we handle media. We literally own it and yet let cultural ideals of norms dictate who we relate to. Just like in real life, anyone could be trans and not state it. It's a status, not necessarily a lifestyle.)