Okay but like, unironically I have Theories(tm) about this, as an ace-as-fuck prose writer, and the theories all essentially boil down to: fish don't have a word for water.
Like, the allos just take a look at something and KNOW it's hot, but the aces have to fucking DISSECT the thing to figure out wtf people are even going on about with calling it "hot", and funny story, turns out when you write a whole-ass 10k of PWP explaining what's hot about the thing in a way that makes sense to you personally, you are a whole lot likelier to make that thing read AS hot to people who normally would not think it was even remotely appealing ( and also, like, to take anybody who was already into the thing out at the knee ).
( see: everyone who has ever told me "I HATE this kink/that kink/this pairing/this genre/this trend, but when YOU write it--" )
And especially in prose, the dissection-explanation gets you into the mood of the scene/head of the character a lot better, while if you DON'T have the dissection worked out but also don't have the crutch of any visual aids to point to, well, then people are a lot less likely to instinctively understand what YOU instinctively understand, even if everyone in the conversation is the same sexuality/has the same tastes/etc etc etc.
So basically, if you're an allo, you probably have not actually HAD to spend that much time breaking down "why is this person/behavior/situation hot to me" unless you just felt like doing it; if you don't bother, though, you don't stop being able to look at something and go "that's hot". Because you just KNOW it's hot; it's like an instinct or a talent, and it's just immediately THERE, before you even necessarily fully know what it really is or develop it at all. You KNOW it's hot, and you don't get why anyone else would need that explained to them when it is just so damn OBVIOUS. You're immediately good at understanding it in yourself, but you don't necessarily understand it in a way where you can explain it to someone else; you haven't put in the practice or developed the thoughts, because you didn't need to, they were already just THERE.
But the thing with prose is you can't just point at the thing and be like "SEE?!??"; you've gotta figure out how to actually EXPLAIN the thing to people, and I feel like that can be a longer process for an allosexual person because they don't necessarily get what it is that they have to explain in the same way an asexual who's starting from ground zero does. The ace person already knows they don't know any of this shit, and knows there's other people who won't get it either, both ace AND allo. The natural talent, meanwhile, is just like "but it's so OBVIOUS, why don't you just GET it??" THEY get it, after all; it's OBVIOUS!!
So yeah, I would like to present, again, my hypothesis/thesis: fish don't have a word for water, but you are currently addressing a semi-aquatic mammal, and man, let me tell you about the water CYCLE.