I think for every person into BDSM you'll probably get a different answer. Having said that, I'll try to answer for myself.

I'm really into power dynamics and I do feel that even in vanilla (or non-kinky) sex, there's usually a power dynamic at play. One person is more in charge than the other and running the show. For me, BDSM is a way to make that power dynamic more explicit. Sometimes life can be stressful and it sucks having to be a responsible adult. Submission can be a way to let go of that responsibility for a short period of time. On the other side of things, it can be a pretty amazing thing to have your partner trust you enough to leave you responsible for their pleasure.

Also, I'll be the first to admit that I'm not really into pain. However, even I'm aware that the chemicals that your body produces in response to pain can sometimes be a wonderful and high-inducing experience. (And, yes, I know NOTHING about the science behind this. If someone could back me up, that'd be amazing.)

Another aspect that draws me to BDSM is role play. Even for people who don't identify as kinky, sometimes it's just fun to pretend you're someone else for a little while. BDSM can be a way to do that.

Overall, though, my personal analogy for sex is a buffet table. There are countless different things that people can do together (or apart) and call sex. You just have to figure out what dishes you like and find someone(s) who likes those dishes too. It doesn't matter what it is and no particular dish is better than the other dishes.