IMO, it's a fetish, like a foot fetish or a panty fetish. But it's not only very ugly, but also much more dangerous, because (a) it spreads fatal diseases, (b) it is self-propagating (no panties are running around trying to get impressionable minors to 'play' with them).
I assisted in an theft investigation of patient casting materials at the hospital in which I worked at the time. Turns out, we had an employee (in an patient greeter type position) stealing casting materials and passing himself off as a physician at some other hospitals in order to get his hands on the same from their stock.
In the interview, he disclosed that he suffered from a fetish that compelled him to place a cast on an arm or leg and then sexually gratify himself.
What was told to me by the social worker called in to assist us: That there were approximately .75% of the population "afflicted with this fetish." She recited other percentages of persons afflicted with other fetishes. I asked her how many persons were thought to be homosexual. She responded with the 2-4% number.
I asked her why all of the protections afforded gays versus other sexual proclivities or fetishes. Her simple reply, "They have a better lobby. A big enough percentage of people who make the rules are gay."