Earlier quoted context omitted.
If you're the kind of person who throws away plastic bags and doesn't re-use them as trash bags, please have the decency to cut the handles. Do your cotton bags have over 5000 trips to the grocery store over the last decade? If not, you may be carbon negative compared to single-use plastic bags (not counting the re-usability as trash bags).
Meanwhile on this planet, the micron thick Walmart plastic plastic bags are not usefully reused as trashbags; and neither are most of the others. I don't really have a use in general for plastic bags that small and fragile except maybe in the car from time to time. To a first approximation, no one is cutting the handles and, even if they don't just toss them on the road, plenty of them surely end up blowing away out…
I agree that nobody is cutting the handles, but the reuse is a lot more prolific than you think. Even so, they are indisputably more environmentally friendly than cotton bags.