Okay, BDSM is weird. Why would someone want to do this stuff?
This is a common question, but it's not easy to answer beyond just "different people have different tastes." I love broccoli. Other people hate broccoli. Why? Different people have different tastes.
There can be a desire, when it comes to sex, to understand why we do the things we do. A lot of this desire comes from the misguided notion that there is such a thing as "normal" sex, and there must be a reason people deviate from what's "normal."
In reality, there really is no such thing as normal when it comes to human sexuality. People who talk about "normal" sex probably have a picture in their heads of what that looks like. Maybe it's missionary-position heterosexual penis-in-vagina intercourse with the lights out. Or whatever.
But the fact is, humans have always engaged in a huge variety of different sexual activities. Unless you live in a remote cabin far in the wilderness, right now there are probably people having sex in all kinds of ways somewhere within a few miles of you that you would not consider "normal," and that's totally the norm for human beings. Yes, even in conservative countries. All kinds of things are a normal part of the human sexual experience--PiV intercourse, oral sex, anal sex, sex between more than two people, and yes, even kinky sex. All of it normal and ordinary parts of the human sexual condition from the dawn of time.
When it comes to sex, there is no such thing as normal,, just as there is no such thing as "normal" food.
Hang on a minute! There must be something wrong with people who like being spanked or whipped. That can't be normal! Were they abused as kids, to like such a thing?
I mean, sure, if you look you can find people in the BDSM scene who have suffered abuse or trauma, just like you can find accountants, doctors, redheads, politicians, conservative religious people, dog owners, and lumberjacks who have suffered abuse or trauma. If you examine a large enough group of people, some of them will have trauma in their backgrounds.
But it's not trauma that makes someone kinky, any more than it's trauma that makes someone a redhead or makes someone a lumberjack.
In fact, studies have shown that BDSM practitioners are generally psychologically healthier, not less healthy, than baseline.
But being whipped! Why would someone want something that hurts?
Do you have a friend who likes spicy food?
I don't mean the person who orders Thai food with spices. I mean a person who really likes spicy food. The person who says "give me all the spices you normally put in your hottest meal and then add all the spices that my buddy here doesn't want." The person who not only knows all the varieties of chili pepper but can name them on sight and rank them by heat. The person for whom five-alarm chili is just a warmup.
I have a friend like that. He was a roommate in my college days. I've seen him eat, and man, it looks painful. Even thinking about it makes me wince.
And yet, nobody ever asks him, "why on earth would you want an experience like having chemical burns? What happened to you in childhood that makes you seek after the culinary equivalent of Medieval torture? Why in the name of all that is holy would you eat something that makes you cry?
When it comes to things outside of sex, we understand that different people have different tastes and that doesn't mean trauma or a bad childhood. We don't search for hidden abuse in people who gravitate toward the chili cook-off table at a county fair. Different folks have different tastes and there doesn't have to be a reason for it.
We think sex is different largely because we know there's no such thing as "normal" taste in food but we still hang on to the idea that there is a "normal" sexual experience.
This extends to all sorts of other things. Rock climbers expect to get banged up; it's part of the hobby. You don't climb rocks without aches and pains and bruises. But we never hear anyone say "you do a sport that means you get bruised? What happened to you during your formative years?" And sure, you can say that the point of rock climbing isn't the bruise, it's the experience...but that's true of BDSM as well! The bruises are just nice mementos.
Still, craving pain for its own sake has got to be weird, right?
If you ask that chili aficionado why he craves the sensation of chemical burns, he'll probably look at you a bit strangely.
Perhaps a key to understanding this is that it's intensity, not pain for its own sake, that matters. People into BDSM like intense experiences. Lots of people like intense experiences; some of them simply like that intensity in the bedroom (or on the kitchen counter or wherever). Thinking about it in terms if intensity will, I think, get you further in understanding why someone might be drawn to BDSM than thinking about it in terms of pain.