Is it greed? Or is it a mental pathology, like sadism?
Animal-fighting experts and two former dogfighters offered a variety of insights in interviews, but all agreed on one thing: the attraction is intense.
"It's an addiction that's hard to get away from," said a former Philadelphia dogfighter who now feels remorse but still remembers the pull of breeding, raising, training and fighting pit bulls.
"It's the thrill of knowing things most people don't know, learning the business, the ego, the challenge," the dogfighter said.
Veteran dogmen become so immersed in the business, experts say, that it becomes an obsession.
"A lot of these dogfighters couldn't tell you their first son's birthday, but know the pedigree of every dog in their yard," said John Goodwin, of the Humane Society.
Among urban dogfighters, owning a menacing pit bull affords a street-tough status, an image reinforced by rap artists like DMX, who used dogfighting imagery in his work and was ultimately imprisoned for animal cruelty.
And two ex-dogfighters said that there is a kind of love between a dog owner and the animal he trains for mortal combat.
Former Chicago dogfighter Sean Moore said that he wept over dogs injured or killed in fights. "It's hard to explain," he said, "but you love your dog and train him to put him in a place where he can win, like a trainer getting his boxer ready to fight Muhammad Ali."
But Moore said that love turns to anger when a dog loses.
The former Philadelphia-area dogfighter learned to think of fighting dogs differently from pets: "The deeper you get into it, you love the animals, but it comes where you consider them livestock, because if the dog quits, you have to do one of two things - give the dog away, or have someone put the dog down.
"I wasn't attached to the fighting dogs," the dogfighter said. "The dogs crave attention. And - this is years ago, I couldn't see myself doing this today - but I'd give them the attention they need as long as they'd perform for me."
ASPCA psychologist Randall Lockwood said that gambling addiction and greed are part of the culture, and there's a streak of sadism in many dogfighters. "When we see folks involved in animal cruelty, a lot of it is about power and control and a sense of accomplishment through your animals," he said.
"As long as the dog is winning, the dogfighter loves his animal," said Tio Hardiman, who works in a Chicago anti-dogfighting program. "But when the dog goes on a losing streak, they end up killing him, so it's a bulls--t love affair."
"I can't believe what I've done, things that seem so cruel now," the Philadelphia dogfighter said. "To this day I have nightmares over what I've done."