IMO, as a guy who is VERY sexual, I know that fetishes are mostly a result of the human, male especially, evolutionary need for variety in sexual partners. We were not originally evolving to be monogamous creatures. It was in our best interest, as individuals and as a species, to sleep around and sleep around as much as possible. The desire for sexual variety is based in such simple evolutionary needs. We really over complicate things a lot these days. Think about it and it makes so much sense and explains so many things. Other environmental factors certainly play a role as well. What we're, boys especially, are exposed to during those early adolescent years when our hormones start to go nuts has a profound impact us as we age.