Great post, Cassie.
Too many people like the way it is now, for it to change.
Too many people like the convention of not asking a host to put themselves out further, for the picky needs of one individual.
The way it has been explained numerous times on this thread (and I'm guessing on the other; I haven't read it) suggests that if you haven't got it by now, you never will.
But you won't change the way it is, because the current norms work too well for the majority.
I'm not British, but I moved there in my early twenties and lived there for over a decade. Our social interaction framework is reasonably similar, but perhaps not quite as pronounced and nuanced as the British version.
I found the social conventions something I was able to slip into with great ease. They suit me. I'm a people-pleaser, gregarious, I loathe confrontation, I'm sensitive, very intuitive and empathetic. I hate other people feeling uncomfortable in my presence, will go to great lengths to avoid it, and will quietly form judgments about (and distance myself from) people who don't comply. And no, I wouldn't invite you back for dinner either, and I certainly would not explain why. I'd just move on from the acquaintance-ship, and concentrate on other friends.
I find the idea of the world you paint, with people just coming out and asking - and annoying people left, right and centre - deeply uncomfortable and unpleasant! I won't be switching to your model any time soon.
You think your way is preferable. Clearly too many others do not, hence why we have the set-up we have. You don't have to understand it.