As we entered the national parks in the Sierras (Sequoia, Kings Canyon, and Yosemite) the importance of proper food storage became even more important. More visitors to parks, more food, more possible interactions itch bears or other wildlife. You DONT want an animal getting at your food! Not only will you have nothing to eat (the horror!) but the animals will become acclimated to eating human food, more likely to attack humans, and then may have to be destroyed by the Rangers. No park ranger wants to kill a bear!
And that's why there are the bear canisters. Bear canisters are hard containers that bears and mice and marmots are unable to get into. There are other options- I've been carrying an URsack, an animal proof bag that can be punctured but not ripped open. You have to tie it a special way to make sure the animals can't open it. But the URsack is not approved for use in some parts of Sequioia and Kings Canyon or any of Yosemite. So a bear canister is needed.
Here's the deal- they're bulky. And awkward. And a little heavy. Everyone hates them. I mean, we don't want the Bears to get killed. But we don't like the bear canisters.
When you are backpacking, you do not CARRY a backpack. You WEAR a backpack. You need a pack that fits you well, accommodates your waist size, torso length, shoulder width. Something that is adjustable to your inevitable weight loss. And you need to experiment to figure out the best way to pack your gear do that the weight of your pack is distributed in a similar way to your body's weight distribution. That way, your pack molds to you, moves with you, almost becomes part of you.
A bear canister does not mold to you. A bear canister takes up room in your pack and leaves weird empty spaces. A bear canister does not move with you, but shifts as a unit, making your pack swat. With a bear box, you do not WEAR a backpack, you CARRY it.
Which is why I made the decision in Lone Pine to mail my bear canister ahead and use it only in Yosemite. There were bear lockers in the campsites where the canisters were required, and I'd just make sure to camp where there were lockers. That way, I wouldn't be climbing over 12 and 13,000 foot passes while CARRYING a backpack, but instead while WEARING one. It may seem like a subtle difference, but above 10,000 feet, it can be huge!