A friend of mine has an 18 year old daughter. The family doesn't have churchy values. They're more of a love, let live, trust yourself group. The daughter recently had a close encounter on the 2nd date, and the cops called mom. Ack! Mom doesn't seem to care if daughter does those things whenever she wants to, but doesn't want some boy pressuring her to do those things.
I come from the perspective that you should be married, in the temple before all that. And I think that having parents expect that of you is good for kids. And also having parents that understand if things don't go that way, is good too. How do you be the father that embraces the prodigal? Wow.
An analogy that I came up with was a fire extinguisher. It's a useful tool but we put it behind a pane of glass so that nobody makes a mess of things because they were bored. The glass can be broken anytime someone really wants the fire extinguisher enough to break the glass. But you don't just leave the fire extinguisher out. It'll get used.
I hope our children choose marriage and safe environments for having children. Even if they don't choose that, they should understand that it's their choice, not their "friend" who gets to choose. They should have known the person for 2 months minimum. They should have met each set of parents. They should decide that they are going to do those things, not just fumble into it one night that they are bored.
I think the same goes for kids getting married. If a kid wants to marry a person they've only known for a few weeks, and they want a wedding in a month, I'll say, "Woah!" But I'd rather they get married fast, than wait for temptation to play it's self out.