Forgetting to pack the reusable cloth bags back in the car, thinking ahead. But when we do forget them, we try to keep as many things out of bags as possible. It's really a habit that's hard to break. The other day in a store some guy insisted on putting two bags on something even though I asked him not to! He just couldn't stop himself.
Then a few stores around here won't use them at all but many are working hard offering alternatives.
But like many here, we reuse them for other things, but they still end up in the trash.
I'm waiting for some nut to go ballistic in a parking lot somewhere shooting the people festooned with goods in plastic bags, leaving the cloth bag people alone.