No, really, a lot of people just don't ever click on ads. They don't even really see the ads. There are sometimes parts of websites that I subconsciously filter out because I'm used to seeing ads in that area or they've made that bit look a bit too much like an ad.
For more extreme view-points there's the Boulder Pledge, and some people really do see any form of advertising as a type of spam. Like I say, this is a minority extreme viewpoint, but it does exist.