I mean, that’s kind of a hard question to pin down in any sort of specific fashion. I suppose the easiest way to answer that is to say that I find the things pigs generally signify erotic: sloth, gluttony, obesity, filth. None of that really maps onto pigs as they actually exist–they’re actually very smart, quite clean, and super adorable!

Especially kune kune pigs, so fluffy!

They’re my husband’s favorite pig breed. He finally got to pet one at the state fair this year–it was very emotional.
Back to more serious matters, I think that the “furry” aspect of stories depends a lot on the individual person, and the kinds of species people prefer tend to be odd. For example, I just don’t have any real erotic interest in canines, which is part of the reason pup stories are relatively few and far between. Same with donkeys and other equine animals. That isn’t the say that I don’t *understand* the erotic appeal of them (which is what lets me get away with writing them at all, I think), but that the whole pup thing just doesn’t interest me that much. This is also why it’s a bit hard to explain.
It’s easy to describe the…I suppose we could call them “reasons” why people find pigs erotic and identify with them, but the actual erotic desire is a lot deeper than than, and doesn’t necessarily map onto those reasons neatly. I just like pigmen, I suppose, and I can rationalize at least some of the reasons why I like them, but most of the attraction is just…there.