Because Wiltshire has a large concentration of ancient monuments, it also has a large concentration of misguided people who think that they know what these ancient sites were for and the religions that attended them. These poor folk also think crop circles are some how mystical. The folk who make the crop circles either make them to prove their theory, or make them to laugh at the misguided people, or make them to make money from the tourism and so make them where the misguided people congregate.
See what I mean???
Alien Heaven indeed.