This demonstrates an element of character development and part of the enjoyment(?), or at least a necessary process, in drawing one into an AVN and investing in the character and the story - past, present and future. If everything was plain, simple and "black and white", there would be nothing to hold you're attention (unless you're only in it for the lewds).
Reality is often vague and hard to get a grip on - sometimes you want to escape that and is why we have sports, entertainment (wait, those are bad examples these days...

), but such things don't hold your attention or feed your mind very long or very much. Unraveling a character and a story (that has occasional and well done sexy scenes) helps to feed AND entertain the brain. Somehow, to me at least, that is more fulfilling and enjoyable than "meet LI1, fuck LI1; meet LI2 fuck LI2 etc.," so on, so forth until the second round with each when you add anal to the mix. Many of these AVNs are so damn predictable - that's why I like the ones more like the books I read - there's an element that makes you think and use your brain.
Maybe I went off on a little bit of a tangent or this response seems like a
non sequitur, but it is what came to my mind (it has very few straight lines). Basically, without a little bit of confusion at times, stories and characters get too predictable and just aren't worth the time - leave 2D characters for 2D stories; give 3D stories 3D characters, ambiguities and all.