This is just my thought, but the people that used to shop Walmart now shop at dollar stores and any other place they can get needed goods for the cheapest possible price.
Dollar General, on the other hand, has smaller stores in every little burg, they're close by. Selection is much thinner but prices are just as good if not better, and it's handy.
I'd never set foot in a dollar store until 2008, now I buy most of my incidental stuff there, it's a mile away and right on my commute. I hit an actual grocery store, in my case Food Lion, once, maybe twice a month at most. Meats, produce, the things a Dollar General does not stock.
It can be sort of depressing, because the poorest of the poor do shop there, especially on Saturday with the $5.00 off coupon on a $25.00 purchase. But, it works. So, I continue to do it. There are lines at their checkout now, which is a relatively new thing.