I recently found what is possibly the best explanation for why we travel that I've ever seen. The article, by New Yorker ace Burkhard Bilger, is about a neuroscientist's research into how the brain perceives time. The piece contains little, if any, discussion about travel per se. Yet when I read this passage, I immediately thought about what it means to go places.
One of the seats of emotion and memory in the brain is the amygdala, he explained. When something threatens your life, this area seems to kick into overdrive, recording every last detail of the experience. The more detailed the memory, the longer the moment seems to last. "This explains why we think that time speeds up when we grow older," Eagleman said--why childhood summers seem to go on forever, while old age slips by while we're dozing. The more familiar the world becomes, the less information your brain writes down, and the more quickly time seems to pass.
Travel keeps things unfamiliar. Keep exploring unfamiliar terrain and seeking novel experiences, and your brain will write down more information, at least according to this theory. Perhaps it even creates the impression that time isn't passing us by quite so damn fast.