Why do women hide facts about number of past sexual partners?

To avoid a label: Some people feel that a woman that has had more than 1 sexual partner is sexually promiscuous, aka a "slut". Furthermore, some people think that a sexually inexperienced woman would make a better sexual partner due to a tighter vagina. These are myths or cultural biases that have nothing to do with reality. But perceptions and opinions don't change easily. So some women hide the number.