Couple of thoughts...
I was demonstrating proper use of spray to my wife about 15 years ago and deployed a small burst from a can. A gentle breeze blew some back at me and rendered me blind, moaning, and helpless. (to the great amusement of my wife

)
I stopped carrying it for several years after that and carried only my .44.
I was charged at close range by a huge boar, that ended up running right by me. I froze and didn't even unholster my weapon..... Luckily the "charge" was really just the bear breaking into a bluff run by me. But it left me feeling a little flat footed and underprepared. Also, had I killed that bear, it would have been wrong. He was not attacking, just bluffing.
Recently I have gone back to carrying both.... The research and numbers just don't lie. But many of the reasons for both are well spelled out by Kevin.
1)We are way back in grizzly country for multiple day hunts. Seeing a grizzly is a very real possibility. Also, these are not your fat, happy, fish eating alaska bears. These are the snarling survivors, that scratch an existence living partly on moths and robbing squirrels. I.e. they have a hungry belly and a chip on their shoulders.
2) Some times in camp a weapon is the right tool for warning or a long range deterent.
3) I like the idea of spray first... shoot him off me if need be.
Jeff