The problem there is that the law didn't define "reusable" bags well enough, so stores just made slightly thicker plastic bags and called them reusable even though they really aren't. As a result people ended up using the same amount of bags but with far more plastic.
I see the benefit of those heavier “reusable” bags as coming from the fact that they are less likely to blow away and get into the waterways. If you drop one it is more likely to be picked up and put in to the trash instead of ending up in a turtle’s breakfast.
