Hymens

I was thinking about hymens for a while now. More specifically, about the fact that a certain percentage of women don't have a hymen to begin with versus the fact that some cultures require them to.

I am wondering:

1. How high is the percentage of women who do not have a hymen to begin with? I mean "do not have a hymen" in the sense of not having enough of a hymen to bleed during their first intercourse.

2. Does it vary by ethnic group and culture? One could think that in a culture where a non-virgin bride was generally killed eventually there would be fewer women born without a hymen than, say, in a culture where a non-virgin bride was generally given back to her parents and then married off to some poor guy who could not afford a virgin.

3. In the cultures where virginity is still very important how well is the population aware that a significant percentage of virgins do not have a hymen? Are men aware of it? Women? Young girls?

4. What do they do? Do they get in trouble for not being a virgin? Do they check whether or not they have a hymen and arrange for some blood somewhere if they don't? If yes, do girls take care of that? Do their mothers?

5. Why does western literaure on the subject tend to emphasize sports and tampon usage as hymen-stretching factors, as opposed to people just being born that way? Is it because that is indeed the case, or are there some social reasons for this emphasis?

6. Why don't people in western cultures usually just have their hymen cut by a gynecologist if they have one, instead of waiting for their first intercourse to be messy and painful?