After years of contributing to Google for free, I continue to do it because I am supporting a system I use on a daily basis. This is reinforced by the fact that I now live in a small town that often does not have as much content online as your big cities do. With a high tourist rate due to the city being formed around a major university, I hope to do my part in reducing the frustration of traveling through a town and not having access to good reviews, photos, and even map directions to local hot spots.
I am passionate about doing this because I, myself, am a frequent traveling and I often seek out small towns to spend a day or two getting to know the local culture. I know personally how frustrating it is for those of us that are used to having reviews on Google maps to arrive in a town with little to no available data.