The campsites are filtered to within 10 miles of a gym so in that case, ya, since they tend to be in cities. Overall, there are a lot more campsites than gyms, only sixty something gyms and like five hundred free campsites in Washington based on the data I'm using.
I'm looking into having it recommend areas to check out even if there is no campsite data. For example, if there is a national forest boundary where free camping is allowed within the specified distance of a gym, show that. Then you could look more closely at those areas for roads with pull offs and stuff.