When traveling with friends or family it creates memories for a lifetime.
These memories will create a bond that nothing can erase no matter what happens with the friendship/relationship. It can also give a new perspective on the relationship and cement the bond forever. It also gives nice stories to tell people afterwards, you can create photo albums about your trips and when you feel nostalgic you can take an hour of your life and experience the trips again by looking at your pictures.
Traveling gives us the opportunity to disconnect from our regular life.
You get to forget your problems/issues for a few weeks, it can also help you figure things out that you would not have understood without the distance traveling can give you. We all have crazy schedules, work and a family to take care of, going away alone or with some friends can give you distance and perhaps even make you realize how important these people are for you. Like the saying says: we never know what we have until we lose it.