Waiting for midnight, spike in hungry families on food stamps at Walmart (2011)

In the other 43 states, different people will have different issuance dates depending on last name/SSN/case number.

On the one hand, using the same day for eyeryone gives stores the opportunity to make sure they are fully-stocked before the "surge"; on the other, and from personal experience, having the days spread out usually means you don't have to choose between lining up at midnight, or waiting a few days for the shelves to be restocked.