Why is wheel shaking common in most shopping carts?

Question

I've been to most supermarkets and i notice most of the shopping carts have wheel shaking. Why is it so common in shopping carts?

Answer 1

The problem is that the carts are used so often by so many people. The shaking is just wear 'n' tear. Have you ever noticed how badly people will turn the carts to get into an aisle or when they pull them sideways to make more room for someone in an aisle.