The thing about this is, I've seen a ton of slash that isn't just an excuse for porn, and just as much het that is. Some people... enjoy porn. Other people really like the emotions and personalities and relationships. I'm a lesbian myself, and I find that what you're describing is just a quality of fandom overall, not just slash shippers.

And I'm just gonna add to that, that I don't really want to see oh-so-serious fanfics and such most of the time. Too many movies and books about gay people only play up the depressing aspects, with so much torture and hardship and angst and unhappy endings. If I wanted that, I'd watch Brokeback Mountain. I don't actually want to see that movie because I don't enjoy that sort of depressing message and storyline; in fandom, I want to read and write about relationships I find to be interesting and fun.