My experiences have been quite different. I am bear bait. I regularly encounter bears, in ALL parts of the Sierra as well as on the coast (Lost Coast). My most serious up-close bear stand-off was in Sequoia- bear and I stared each other down and talked it over for half an hour before she let me pass (she had a cub). Often I run into two or more bears a day. One 3-day trip I ran into 8 bears. Most of these encounters are off-trail and during the day. I have also had a bear roll my bear cannister around in the Wind River Mountains of Wyoming.
I think a lot of people think they see no bears because they really do not look for them. A am constantly looking for bears. When there are bear sign, I start calmly talking to them (last spring when I ran into tons of bear tracks I recited Dr Seuss stories to them).
I do think the cannister requirement is working - each year I see fewer bears.
Bears in the Sierra raid camps at night in areas of heavy use. I seldom camp in heavily used areas. You are more likely to run into a bear in the day off-trail. Bears really do not want to be around you - just make a lot of noise or talk (or sing)and they usually get off the trail. I also clank my trekking poles in such a manner that I sound like two people and talk in two voices so I sound like two people.
Some protocols when backpacking in bear country:
Keep a clean camp. Wash hands and face before going to bed. Ideally cook in area well away from tent. In fact in grizzly country, it is a good idea to cook and then travel another mile to camp.
Avoid packer's camps or established camps.
Keep an eye out for bear signs- learn to recognize bear poo, berry stains on rocks, bear fuzz on bushes, tracks. If you smell a bear they are really close!
Choose campsite well over a mile from any fresh bear sign.
Do not take excessively smelly food. I never take bacon, jerky or other very smelly food if I anticipate lots of bears.
Make lots of noise when walking.
Safer to travel in groups, not solo.
Always look around. Never get between mother and cub. (All mother/cubs I have encountered - mother sent cubs up tree and she stood on hind legs and growled. I backed off slowly.)
There is disagreement on fires. Some say campfires attract bears. My experience has been that if I build a fire, bears stay the distance. Bears smell really well - if they are near they can smell you anyway. But they should be a bit fearful of fires.
If a black bear gets into camp, run them off. If they attack, fight back.