I just never stopped using them since childhood. Why would I give up on it? It’s ergonomic, it relies on strong spinal muscles allowing one to carry heavier weight, keeps one’s hands free and unloaded, doesn’t press against one’s neck like shoulder bags do, and is very hard for someone malicious to take off someone.

The only downsides I can see is that I cannot keep it in sight, meaning I should mind my surroundings not to hit anyone, and it can also be opened without me noticing (although Bobby bags solve this in particular).