Why do people have pet cats?

[conuly]

I don't mean "why do people keep pet cats now", that's self-evident, cats are wonderful little foot warmers. And I don't mean "how were cats domesticated" because I already know all about that and I think self-domesticating felines are awesome.

I mean "what caused the transition between useful critter and pet?"

Was it a bet?

"Hey, you know those furry things that hang around granaries?"
"Mice and rats?"
"No, the ones that EAT mice and rats."
"What about them?"
"Bet you a pound of copper you can't grab one, rub your hands all over it, and come out again without getting bit!"
"... You're on. But if I win, you have to eat this solid milk stuff that grew in that cow stomach I was using for a bag, and I bet YOU can't do it without vomiting."
"Ugh. Fine, but when I do, you're going to have to drink this rotten grape juice."

The next day...

"So? What happened?
"You won't believe this, but when I picked it up it started VIBRATING! Is that weird or what?"
"But it didn't bite you? Damn."

I mean, seriously, hadn't the ancients ever heard not to harass wild animals?