I'm pretty sure the same way animal people appeals to some. Semi-random, sometimes based on a particular early-life experience.
One hypothesis for the prevalence of foot fetishism (the most common fetish) is that, since the regions of the brain that process sensory information from the feet is adjacent to the area processing information from the genitals, an association is liable to be formed between feet and sex.
You and I both know where the prudishness comes from.
They're not getting laid! It makes you cranky and a killjoy.
Does any one remember Wolf Kids?
Well, I used to call them Wolf Kids. You know the teenage-ish kids who walk around in public with tails on. And not in public where it would be apporpiate, like let's say a convention center or a Renissance faire.
I just saw a teenage-ish girl at Subway yesterday who I would say is a Wolf Kid. I first noticed she had a hoodie with ears on the hood. I didn't really think much of it, they are kind of common now, (would love one with little devil horns personally), but then I noticed a little grey fuzzy tail poking out under the hoodie.