Including some of the desirable men many women are looking for commitment. Some of the women they're related to may also be critical about it (ie: mother, sister, friends, other competing women, etc). This has lead to some women feeling the need to be less than honest about their sexual history in order to avoid messing up their chances with said men.
I'm not condoning the perspective, but there it is and there's not much that can be done to change it. Just as modern women get to have arbitrary standards, so do the men.
Who the hell is running to their family members to let them know they fucked on the first date? ---
I love catching people in the act. That's why I whip open doors.