Because the magic number is 6. The rate of divorce skyrockets of women that have had more than 6 sexual partners.
@SW15 had the stuE="pipeman84, post: 3104587, member: 160629"]
Take a 25yrs old girl who's had 4 boyfriends during the past 9 years. Many would say, wife material right there. But let's think logically, how is she going to handle the challenges of marriage and having kids, when she couldn't hold on to any of the 4 boyfriends? That means she's either too dumb in picking them and/or lacks loyalty and/or has some deep seated issues that chase the guys away.
The marriage might not end in divorce, so you don't see cases like her in the statistics. And again, I'm asking you to think logically: why is that? Because 1. she's made such a giant leap in self development that all the problems mentioned above have disappeared or 2. out of necessity: ie, she's older now, wants to fulfil the social circle expectations, has kids and needs the help and extra income etc.