(This got buried in my inbox, sorry for the late reply)
I don’t know if I have a satisfying answer for this question. Part of my hesitance in answering is that I’m not quite sure what you mean by ‘associate’ in this context. However, I can answer a simpler question that I think is related to your overall query, which is simply, why do I write this stuff? Not just why do I write porn, but why do I write so many different styles, fetishes, and genres. I don’t think this is quite what you wanted to know, but maybe it’ll cast a light.
As I have mentioned before, I’m a philosopher by education. This is part of where I get my inspiration, and part of why I write these things. Central to my stories are two questions:
1) what does it mean to be human? At what point do our sexual drives overwhelm our basic humanity, autonomy, and conscience?
2) What does it mean to be the same person over time? Can someone change so radically that they retain the same body, and yet are someone else mentally? How do people react to this sort of ‘death’?
There’s more than two questions there, I know, shut up. They all rephrase the same two ideas though, one about human nature, and one about personal identity. Both of these topics fascinated me before I started writing this stuff, and are part of what attracts me to the MC/TF genre.
So, what do I want out of them? I want answers to those questions. I just also get to write about sexy-times while I do it, because that’s fun too. I find sex to be very close to both of those questions, because I think a crucial aspect of out humanity and personality is sexual, something which I think a lot of people might disagree with, but that’s my own take on things. I write about such a range, because to me they are all, in the end, variations on the same theme. Also, I like lots of fetishes, so there’s that too.
I hope that answered some of what you had in mind, if not, feel free to ask again.