Glory
It's tough to argue that any other career features as much glory as this one. You're as close as we've got to a superhero. Plus, you get to slide down a pole to go to work. That's pretty glorious.
Just as firefighters don't do this for the money, they also don't do this for the glory. It's certainly a nice side benefit; after all, they're only human, and expressions of gratitude and admiration can make them feel validated in their life's purpose. But the premier motivation is the protecting of citizens. Besides, the public can't bestow upon you those expressions of gratitude and admiration unless you save them in the first place.