I mean, it's targeted manipulation of pressure points in human psychology. If it never worked, they'd adopt different unethical tactics.

That said, I think you overestimate the level of churn those guys are willing to go through. They'll strike out a lot in rapid succession, burning through the local pool of women until they find one that falls for their gimmicks. When you're willing to take dozens of rejections and settle for anyone moderately physically attractive, yeah, it's easy to keep someone around, just not easy to keep the same someone around.