Question

Why is it preferable to carry shoulder bags that hav broad strap?

Answer 1

We know that pressure is inversely proportional to area i.e. if area will smaller more pressure will be applied and if area is larger less pressure will be felt (assuming that force is same in both conditions).
Therefore to minimise the pressure on our shoulders bags with broad strap are user.

Answer 2

Plastic grocery bags have advantages for retailers and consumers! ... Plastic bags are more durable than paper bags. They are less prone to tearing, easier to carry, and are far more useful in bad weather. Plastic bags are reusable, as trashcan liners, as storage bags, or for picking up after the dog