Why do wild rats bite people at all?

I found this article from Pediatrics, entitled Identification of Risk Factors in Rat Bite Incidents Involving Humans, and it got me wondering why wild rats bite people. Dogs bite because they're frightened or have been trained to be vicious, or are backed into a corner, or whatever. There's kind of a logical sense to a dog bite most of the time, even if it's horrific. But also dogs are predators, right? Bears bite because they're predators or they're protecting their young, or you're pissing them off. They're also much bigger than we are, or at least most of them are bigger than most of us.

Cats don't bite all that much, mostly when they're injured or frightened, or about to have a fight with another cat. My ex husband sustained a nasty bite on his foot when our friend's cat was staying with us and crouched down by the sliding glass door growling at another cat in our yard. The ex shoved the cat with his foot prior to closing the curtains and the cat reacted by biting the hell out of him, a not entirely unexpected chain of events.

Small rodents that are tame usually bite because they haven't been socialized or because you're sticking your hand in their cage, again, frightened and possibly panicky. If you snatched up a wild animal in your hands you would expect it to bite you in an effort to get away, just like you would bite something enormous that snatched you up while you were minding your own business.

But if wild rats tend to be kind of stowaways in your house, eating your food and drinking your water, nesting in your basement or the walls of the first floor of your home, why would they change prey behavior and suddenly attack the much larger hosts while they're sleeping? The article says much of the bite victims are children, less than six years old, but to a rat even a four year old is pretty big. I might have thought the kids were trying to catch the rats, because young kids are attracted to animals and have no sense of wild vs tame and what that means, esp if they've been watching Disney movies, but many of the bites occur during sleep.

As a nation we throw away more than enough food to keep rats going so, despite all the horror films and stories, it's hard to imagine that the rats want to eat those they bite. So why? Anyone know?