That's an interesting question. I've considered the value of these trips as well. I think the best thing about going on an international trip with your classmates is that it's a great chance to really bond. Of course there are many opportunities to get to know your classmates while you're in school. But travelling together, and exploring a new culture together, will give you a chance go get to know these newfound friends in a completely different way.
So maybe five years down the road you're looking for a new job, and you find out your classmate who you travelled with is now the VP at some bank you're interested in working for. So you call him up and say, "Hey Bob, remember the time in Egypt when we rented the dune-buggy and you were driving and you flipped it over and nearly killed us? Boy, those were some crazy times. Anyways, can you hook me up with a job?"
More interesting meaningful experiences will make your friendships stronger and more meaningful and create a stronger network. I know it seems odd to consider "friendships" in such an analytical way, but in the end I think of "networking" as really just making friends, developing relationships where a person is going to be inclined to help you because they like you and vice versa.