I think it’s interesting that the number represents how many different people you’ve had sex with, not how many times. A person’s number could be 3 but if they were in a relationship they could have had ten times the amount of sex as a single person. Wouldn’t this make them more “used” as it were? You’re right. It’s not rational for men to react with judgment about a woman’s number of sexual partners. It’s an emotional response and men are notoriously unskilled at interpreting their emotions.