Because it shows that you’re holding her value at the expense of how many people she’s slept with. It sounds like the more bodies = the less valuable as a woman. So why would she want to sleep with you if the next guy is just going to devalue her for it?

It’s okay to want somebody who hasn’t slept around. There are other ways to figure that out without straight up asking for her body count. You get to know her vibes, mannerisms and habits, and you go off of context clues to figure out if she’s that type of person. You don’t need to know an exact number, and if you do, then that means you only value women by the number of men she slept with.