I wouldn't say it doesn't work. Statistics support both sides. Of course I want to be prepared to defend myself when it doesn't.
The interesting thing about statistics. They'll teach you that spray works in a large percentage of cases. Should you kill a bear, you'll learn that a high percentage of charges are bluffs, and break off at about 20 yards. Shoot a charging bear at 50 yards and you'll hear about that from prosecutors. As I do carry spray, on my left side. And would certainly deploy it, at a longer than 20 yard distance. If the bear breaks through the cloud, I'll need the left to steady my right for the maybe one shot I'll get. But I can't help but wonder if the spray is stopping the bears who were bluffing anyway. And the small percentage who aren't, well, so much for the spray. Wonder if it's a crime to spray a bear orange and making his eyes run.
If you use the bear spray at 20 yards, I don’t see how you would possibly have time to squeeze off one shot at the charging griz.
I'm convinced that the park service is far more interested in protecting bears than they are protecting park visitors. There are plenty of grizzlies in Canada and Alaska. No need to repopulate all the former grizzly habitat in the lower 48. Same with wolves.
[[you’ll learn that a high percentage of charges are bluffs,]]
Except for the ones that aren’t bluffs- not willing to take the chance that it ‘may or may not be a bluff’