Currently, Walmart (and others, but first this) uses HDPE plastics (HDPE is non-biodegradable and can take centuries to decompose.) for their fruits and vegetable sacks. 

These are not returnable nor reusable and go immediately in the waste basket. These are not the collected ones like the plastic sacks for carrying goods home, as they hold foods directly.

It is true they are made as thin as possible but a far greater step can be made.  And made easily.

We have PLA plastics now (PLA products will take up to 6 months to compost in a commercial composting facility.) which is the smart choice for any short time use plastic.  And they are made from a sustainable product as well.  Mostly corn :)

The weight of the bag is 1.9 grams, and typically even I use 3 or 4 per trip getting potatoes, bananas, onions and tomatoes.  It is possible on a big shopping event to use as many as 10; grabbing bell peppers and broccoli and such.  We've all done it if we've shopped.

And a tiny bit of math will show that if Walmart has 1 million grocery shoppers a day, all getting 5 items from the Fruits and Vegetable section, that is 1.9g times 5 million that is 7500 Kilos = 16,534.67 pounds = 8.27 tons a day.  And I'm being conservative.

Customers per week per store ~ Traffic volumes vary greatly, but as a statistical average, about 3500-4000 customers a week shop at a Supercenter. Many stores are in the 10,000+ range. In the US only. ~ quora.com

IT ONLY MAKES SENSE!