Nothing has a 100% infection rate. There are so many things that can happen. The concern is that when something DOES get infected with rabies, it's fatal, and highly contagious. Skunks are often carriers of rabies even if they themselves aren't affect by it. Bats can be too. There is a slight chance the immune system could prevent infection from happening or fight the infection while it's still mild, even without being vaccinated.
I mean, I know my dogs have been exposed to a LOT of things, and while they're vaccinated or inoculated against the majority, I haven't vaccinated for a lot of different things. Kennel cough swept the daycare I was at, and none of my dogs had the vaccine/inoculation for it, and none of the three got it at all. They've had it before, so it's possible it was the same strain, but unlikely.
I just wasn't sure if it was possible to carry rabies without showing symptoms/dying from it, or if it was possible for your immune system to fight it off without the vaccinations that you (humans anyway) can get for it after having been bitten.