I'm chiming in as someone who was on food stamps once upon a time.
First: More rural people are on food stamps than urban. These people are used to making long trips to the nearest town to shop. Rural areas would be a true food desert, IMHO. Urban areas just suffer from inconvenient locations or high price markups.
Second: Minimum wage in my state is over $9 per hours. Working 14 hour days -- even at two jobs so overtime doesn't come into play -- would make most people ineligible for benefits. Many food stamp recipients are actually underemployed, which means they likely aren't working full time hours.
Third: The amount my family received on food stamps was more than twice our normal budget. When we no longer qualified, I had more than $700 still on my card. I allowed it to go back to the state fund because we were no longer unemployed and could pay for our own groceries.
Finally, not everyone but plenty of people are ridiculously dumb about food shopping, independent of food stamp usage. Not a huge deal if you have the cash, but it becomes a problem when you don't. Can't cook or too busy? You could feed a family of four on frozen vegetables and precooked chicken for a month for minimal cost. Most people instead depend on hot pockets, frozen pizzas, "cold" deli foods (uncooked foods allowed by Snap), take n bake pizzas or Subway (cold, thus allowed), and other expensive convenience options.
Many have never learned to use a food budget. The monthly payout for Snap encourages a culture of spend it until it's gone. It shocked me, because many government programs, for example WIC and welfare, require recipients to take at least one class. Food stamps would benefit from requiring at least one class on managing a food budget and how to make a few quick, inexpensive meals. We can raise the amount to $1000 a person, but it won't be enough to feed someone a healthy meal for a month if they don't know the first thing about managing that amount of money. Don't feed me crap about not having time. When you're poor, all you have is time.
So, my belief as someone that has been there, done that? These CEOs need to do it as a month-long challenge so they can see the real problem lies in education and not just the amount. After the education part is implemented, then we can revisit the amount provided.