Learning to be proficient with bear spray is an issue. Most would probably use up the can with the bear too far away. Also, Wind could make the bear spray very difficult to use until they are right on you.
Many people would freeze up on a bear attack. Those that carry a firearm, need to be proficient with that firearm.
It does take time for Bear spray to work, bears can move at a remarkable speed, faster than a horse.
Perhaps bear spray should be used by the National Guard on the Border of Texas, and it would be interesting to see how effective it is.