Why do people carry anything besides a backpack?

Okay, I admit. Satchels and hobos and fine leather look nice. But from a practical standpoint, I just do not see any bag that beats the backpack. Even in the engineering world – and engineers are paid to be practical and realistic – briefcases are the norm (okay okay, there is the occasional renegade). Are we really so obsessed with appearances? What the hell is wrong with a backpack! I’m not saying other types of bags should cease to exist. Rather that backpacks should be socially acceptable in business class rather than deemed sloppy and too casual.

I’d like to know how all the different types of bags evolved into being because they all leave a lot to be desired relative to the backpack. Anything that is meant to go on one shoulder or be held in one hand imposes an imbalance.