They wouldn't have to make another trailer (and they don't like at all) if they just included it in this one. Or the next one.
Anyway you're on point about the sixes/genders having different priorities and interests, seemingly inherently. But IS it inherent? In a way, yes. There are the obvious brain differences between men and women and these have an influence on us from a very young age like there was this one study which showed that boys and girls have a natural inclination towards certain toys shortly after birth. But are these alone to explain the pretty huge differences between men and women and their respective interests? Not... really [especially because of something I'll get to a bit later]?
There's another pretty famous study about societal influence or maybe peer pressure or something. Point is they had people pick which stick or ruler or whatever was longer BUT! the caveat was they had a couple of people say the short stick was longer and the person they tested was always the last to answer and you can guess what happened right? People, vastly, VASTLY, complied with popular opinion. Despite the truth staring them in the face. And the groups saying the short stick was longer didn't even have to be particularly big. Now this is all culture is, a bunch of people saying the short stick is longer. Not to imply that there's a correct answer when it comes to gaming but you get my point yeah? A bunch of people with a slight preference for something precede a general opinion. It snowballs. 'I don't like games' said Susan to Beth, Beth high-fives her and says 'Damn skippy betch neither do I!' they stare expectantly at Ann, Ann actually likes games but now it seems like she shouldn't so 'Yeah home slices games svck.' And so it goes until it becomes a cultural monolith.
Now both of those things (inherent genetic preference + culture) tie into the massive plasticity of our brains. And our brains never stop being malleable, changeable. There's drop off the older you get (I'm not sure how severe) but it never stops. So a common subjective truth gets iterated and iterated and iterated and it becomes a Truth. It gets entrenched in our culture regardless of how broadly true it is or how (like intensity) true it is. And from there it sort of becomes a self-fulfilling prophecy yeah? Because of the malleability of our brains. If it's a cultural more that girls aren't really supposed to play games less of them do, if they don't their brains start trimming those neurons to use their capacity for other, culturally kosher things. When the girl then tries to play games she's 'bad' at them or finds that she's genuinely not interested. Even though she might once have been. We literally fulfill our own expectations. It's a feedback loop and we're holding the ends together.
SO! My point is that if trailers showed female protags more often that would help shift cultural expectations as to what's acceptable (cuz representation. There's reason so many people automatically think 'man' when someone says 'surgeon' but you'd be less inclined to make that automatic connection if you watched a lot Grey's Anatomy), if it shifts cultural expectations it'd allow more girls to play games sans societal judgement which would allow them to form the neural connections guys seemingly have by design (which they do, to an extent [also varying depending on the kind of game] but it's also culturally amplified waaaay beyond what's natural) and thus women who play games would be more common which would mean a larger fanbase for Bethesda and other game devs to make use of. It's kinda a farsighted goal but that doesn't make unrealizable.