Why do people take weddings as such a big deal?

Seriously, thousands of dollars on a wedding? Unless it's a royal wedding, I personally think that marrying someone you love should be fast and simple. I mean, people thes days get engaged after, what, 2 years of dating and put that wedding off another year or so. Islamic weddings take place when a girl is like, 13, not that I think it's right for everyone. But seriusly, I don't seee anything wrong with getting married while your stil in school, as long as it's a good relationship and your respnosible for it. I blive that love can infatuate if you take things faster, not put things off. Besides, it will only encourage aadultery, a sin against God. Wrong!!!