I don't doubt the majority of fatal bear attacks are by Grizzlies/Brown Bears, there shear size and ferociousness when attacking, make it extremely unlikely a unarmed human would be able to fend one off, if playing dead doesn't do the trick. Most people when in their territory are hyper alert, as their reputation probably exceeds the truth for the most part.

Black Bears are a little different. We've all see pictures of the clownish side of black bears. I've seen tourists get out of their cars and pose with black bears foraging on junk food people toss from their cars. 99% of the time it ends peacefully. This just puts the bear and humans in more danger. Humans lose respect for the bears power and wildness, and the bears lose their natural fear of humans.

Algonquin Park has at least 5 fatal black bear attacks, and more than a few near misses.  The most infamous was the 3 teens who were fishing in the park. While the fish they were carrying may have attracted the bear, they fact that it climbed 3 different trees too drag the teens one by one down to kill, proves the Rogue or Predatory bear is rare but not a myth. A couple was killed more recently after the bear attacked he woman and her husband came too her aid with a canoe paddle club.

Fellow paddlers saw the bear dragging one of the corpses around the campsite as the paddled past. When the ranger arrived, the bear still was there, and had fed on the bodies. After killing the bear, they found a pan of ground beef near the fire pit, untouched by the bear. I guess we taste better than beef :o

I carry Bear Spray, but also bring my version of a bear alarm/horn.
Being solo, I worried about leaving my food pack unattended on a 2x portage. I bought a personal alarm, like the runners use. It's the size of a deck of cards and uses a 9 volt battery. Alarm is piercing, like a household fire alarm.

On portages that are especially long, or I see signs of recent bear activity, I secure the lanyard cord to a tree limb, and leave the alarm in a zippered side pocket on my food pack. If a bear grabs pack, the safety pin will be pulled and even if the bear runs off, he/she will have 130+ decibels screaming in their ear ;D

I can't imagine any wild animal tolerating that.  I also take it in tent at night. I would activate it, before using the bear spray as a 2nd to last resort, my camp survival knife being the him or me final option ;)

I figure like most safety items we use, it's better to have it and not need it, than need it and not have it.

The number #1 safety item you can have, is common sense. Unfortunately it doesn't come in a can, and  even if it did, some people wouldn't have sense enough to have a can opener ;D