Environment

I only lived in a walkable city for a few months where I didn't have access to a car, and it was glorious to be able to walk to the grocery store.

But if I was going to the store, I always brought my backpack filled with some reusable bags, since without my backpack I'd be reducing my carrying capacity significantly. It's difficult for me to imagine forgetting to bring my backpack, since I'd have so much time to notice it not being on me on the walk to the store.

With a car it's easier to forget the bags, since they could be out of sight in the trunk, and it's easy not to think about them on the way since driving takes up your focus and attention. But that's just been my experience.

I do like the idea of stores accepting used bags to re-sell (or perhaps a take-a-bag leave-a-bag rack too?) For those who do not have a car and are more forgetful than I.