Six Degrees Of Dialation...

I would like to preface this by saying that these thoughts are not based upon any particular work, nor the works of my flist, rather I have been having a trawl through the good ol' Area 52 and reading a little more fan fiction than I normally would (TV is on repeats and it's nice to curl up with the laptop on these cold winter nights :P).

What is it with this prevalence in slash fiction for having one or both characters express most often than not in a rather drone diatribe their complete sexual history and stance on sexual labels before gettin' down and dirty? It disrupts the flow of narrative, having this sudden recall of events that don't further the story itself but serve only to flesh out these suddenly homosexual characters.

Are these authors feeling as if they have to justify and somehow rationalise placing those characters in a homosexual context? I don't see the point as none of them has expressed completely heterosexual leanings, rather the subtext tends to go screaming in the other direction. :P *cleans fogged slash goggles*

Has anyone written these kinds of back stories for other reasons?