Well for one thing, if you're a guy a condition is getting that dick wet, if nothing else

Women too, though: it's like oh look so many ugly ass guys are dating hotter girls that's unconditional love, or hey look she puts up with so much crap that's unconditional love

Thing is, just because a benefit isn't readily apparent, doesn't mean it's not there. She might be a neurotic mess, and the value she receives is in the form of non-judgmental stability, for example.

Self-sacrifice for its own sake is so rare as to be tHe eXcEpTiOn tHaT prOvEs tHe RulE.