If you look at everything as a perspective, then I and YOU (as well as WE and THEY) are all part of a single mind, so you can think of the whole story as being the inner workings of a single human mind. So the journey of a story is basically one person working through a problem one way (I) while considering whether it might be better to work through it another way (YOU).
Taken this way, YOU is just I as I consider other paths. So if I change, it’s because I considered another path and, more or less, found it compelling enough to do so. In the analogy that is the story, this looks like the IC influencing the MC until the MC changes.
But if I don’t change, it’s because I didn’t find the other path compelling enough and decided to keep solving the problem in the way I already am. At this point I am no longer considering other options. But the YOU perspective doesn’t cease to exist. Instead, it’s like it stops considering other options and considers the option I’ve already chosen. In the story, this looks like the MC remaining steadfast while the IC changes to the MCs perspective.
As someone trying to both write a story and incorporate story theory, it’s frustrating that, in story, there’s a clear influence for the MC to change but not one for the IC. But then there’s already so much about the IC as a character that remains hidden from us because of it being the YOU perspective that it doesn’t seem out of line.