I was convinced I was going to marry the guy I was seeing during my sophomore year in college. Most of us thought that we were going to marry our college sweethearts; ALL of us have moved on to the guy after that and the guy after that one. While it clearly happens, it's not as common as everyone thinks. Of the weddings I've attended in the past 3 years, only one was a couple who started dating while one of them was in college (they met the end of her senior year; he was a few years older). Even then, she went to graduate school and worked for while before they got married. The only other really successful college sweetheart marriages I know of, the couple knew each other in high school.
Some circles promote earlier marriage more than others. Frankly speaking, I think NPC/NIC Greek Life may put "pressure" on people to talk about seriously pairing up younger than the GDI population. There are mixers and candlelightings--who wants to be left out of that? Add to that regional correlates and stigmas about co-habitation, and you have the clear fact that a sorority girl from the South is much more likely to be married at 24 than an independent or NPHC woman who went to college on the East or West coasts.
The right age? Honestly, I think it's when you have an education and are somewhat established in your career. That could be 25 (probably not younger). That could be 35. I don't agree with getting married and starting a family before you can support yourself. Husbands can beat, cheat, and die--you never know when you might be on your own.
Personally, I don't intend on working after I have kids, but I know that I HAVE to work, I can pull a damned good salary and can take care of a family if it comes down to that. A 23 year old with an art history degree who married the first guy she dated in college doesn't have that same insurance.

I hope I don't sound bitter--I'm just old enough now to see people my age getting divorced! Maybe those divorces could have been prevented if they had just waited a minute.