Plastic Grocery Bags

I am regularly disgusted with how dependent people are on plastic bags. Why is it that I can go to the store to purchase two or three items, carry them all over the store, and then it's assumed that once I pay for them I am incapable of carrying them any more? And when you have more than one item, it's amazing how shocked the cashier is when you tell them you don't need a plastic bag. I recognize that it takes a little coordination to carry two or three items at once clear out to my car rather than just hang on to the handles of a bag, but surprisingly, I've been able to manage every time without incident. And I know that it must be really uncommon for people to not use a bag, because every time I go to Walmart the person standing by the door chases me down to make sure I have a receipt. And they can't seem to understand that I just didn't need a bag to carry my three items. If people would just try it — it's really not as difficult as everyone seems to think.