I think it does a lot. My theory is that dominance is a factor in any relationship between any two people, always. We all like to be dominated or dominate. All of us. It's a human thing. As I see it, BDSM'ers have realised this and explored it.
When my non-BDSM friends talk about their relationship problems I can't relate at all. It's as if it's some kind of power struggle where one wins and the other loses. I just don't get it.
I think that under the hood, all humans are into BDSM. Whether they live it or not. What makes us different is that we are the healthy ones. We're the smart crowd who's understood what it's all about and done something about it, instead of whining to our best friends in bars.
And then off-course you've got the people who've understood what it's all about but are just too lazy to do anything about it. Which I guess would be some sort of middle-ground.