(which, in my experience, does appear to be more common in members of the BDSM community, make of that what you will)
It’s what they know. If they were children when it happened, it shaped their view on sex for their entire life. There is no going back from that. You can surprese the feelings, but you really can’t experience sex in any other way… or, you can, but this happens very rarely (very few individuals). They even sometimes see love through that perspective.
Can’t blame them… it’s fucked up, but the best they can do is just move on and do whatever makes them happy, even if it is BDSM.