I think part of the answer may be entrenched social power. If the cool (or rich or athletic) guys have always joined XYZ fraternity, then they will join it next year, even after bad behavior. If XYZ’s parties are where those cool guys are, then that’s where girls who want to meet cool guys will go.
But I thought a lot of colleges had a Greek “system” with some kind of governance beyond individual houses. Why aren’t the good houses more active in sanctioning the bad houses? Is it because the bad houses tend to be the cool ones?
I asked my daughter what girls go to parties at the bad fraternity (after freshman year, anyway), and she said it’s the girls with no self-respect.