The initial question did not have as many choices. Some people added responses that were not on the original list and these were then included in the list of options.
This question indicates that the main reasons that people do geocaching are related to experience and exercise. They also like the thrill of the chase and the sense of achievement in finding difficult caches. So the clue here is to give people a good experience and they will love you.
Interesting to note that people aren't in it for the numbers ... or at least don't want to admit it! We all know people that are obsessed with their cache count and don't worry too much about what the cache is like. However it's obvious that most people enjoy getting out with their friends and family, and enjoying life.
On a side note it appears that geocachers tend to be tech-heads going by the number who like playing with the technology.