Personally I had the same feeling. I was engaged at 19 and couldnt understand the big deal everyone was making. Then I realized that in a very short period of time (like 6 months) I changed a lot about my beliefs etc... and he hadn't. So I think the big idea of it is that at that age, we change A LOT! and I mean a lot. Especially if were in college. We are more into meeting people, finding new things, trying new ideas.... were just all around curious and adventurous at this age which isnt a bad thing. but it also means that theres more room for you to change your mind as to what you want in life. so just because you agree with your mate now on what you want in 5 years, that doesnt mean your ideas and priorities will be the same when it gets to that time. and when you get into your 20s, 30s and past that you are (typically) done with school, you have a pretty good idea of what you want in life and your priorities are pretty in check. so when you find someone who wants the same things as you, its easier to say "this person wants this now, he will probably want the same thing in 5 years."

right now im 21 and I will not get married until Im at least graduated with my B.S. and probably with my M.S. I know that in the field im going into I will do a lot of traveling, meeting new people, taking new classes etc... so Im sure I will change my mind on a lot of things between now and just age 23 or 24. I have done a complete 180 from who I was even a year ago! So I wouldnt trust settling down with someone when I know that I am going to change quite a bit in the near future.

So its not necessarily the money or anything like that. Its a lot of little things that add up. A year ago when I was engaged I was in a different major with different aspirations. So thats just someting to think about.

also, I think that once you get married your outlook kind of changes. even though its just a piece of metal on your finger and a paper at a courthouse, your whole attitude changes. things that you might have wanted to accomplish might not seem so close to home anymore. and I always hate seeing young women give up their dreams because they got married and all of sudden their dreams didnt seem so important anymore. not saying that your fiancee/husband would keep you locked in a dungeon or anything, just throwing that out there.