Why do people say "girls, wait to give your virginity until your married" as if they're going too.?

Infact, why do they try with any teenager, male or female, as if they will? Men (or boys, which ever you prefer) will more often lose their virginity then a woman (or girl, which ever you prefer) and even women lose their virginity at a very young age. I don't understand why people, 99.99% (inaccurate) of whom didn't even stay virgin until they were married either, want kids to stay virgins. Is this just an American thing? I hear (more-less learned from health and gym teachers) most modern countries (Canada, France, Britain, Spain, Sweden, Finland, etc) actually hand out free condoms and birth control (mostly in schools) rather than plead the "youth" for abstinence, and most of my teachers say Americans should do that too, because teens are going to have sex regardless of what we say and they need to be protected not warned and badgered. What's your opinion? (Disregarding that even in Ancient times, Stone age, Dark age, Medieval age, Industrial age, and Modern age, that people started having rough monkey sex as soon as puberty kicked in...) Do adults beg abstinence mostly because that humans now live to their 70's and 80's rather then 20's and 40's? Or is it a moral/religious thing? Again, what's YOUR opinion?