For some people, it was all about some building that inspired them as a child. Perhaps they grew up in some gorgeous mansion. perhaps they went to one of the great museums of the world as a kid and were completely captivated by it. Whatever it was, a single building got them interested in the process of designing and building others.
For other people, architecture schools are part of a political mission. You wouldn't believe how many visionaries there are at an average architectural school. At the one I go to, they probably make up half the class. Some of them want to design buildings with the idea of providing beautiful and affordable housing to the poor, others to change the way we see space as a society.
For me, going to architecture school was part of a much more down to earth experience. As a matter of fact, you could say that I always had an interest in buildings. I grew up on a farm, in one of the last communities in this country that still practices barn raising. For me, architecture school was not the realization of a lifelong abstract dream, but rather a way to build on my early, hands on experiences with communal buildings.
I feel like this gives me a much clearer vision than many people in architecture schools nowadays. Your typical architecture school student has his or her head in the clouds. In some ways, this is a good thing. It is good to have a vision to unify your buildings. There are many things that buildings have to be. They have to be functional, structurally sound, and comfortable to occupy. They don't necessarily have to be beautiful. When they are beautiful, however, it is like a wonderful luxury for the city around. Although not everyone understands an architect's vision, they can tell whether or not he has one.
On the other hand, if you enroll in a school of architecture without any hands-on experience, you can lose track of the purpose behind what you are doing. Architecture is, after all, about providing spaces for people to live and work. Architecture school can teach you many things, but unless you go in with this understanding, you will never build with both elegance and practicality.