Well I did a brief google last night. Seen some people rambling online about free cell phones, free shelter, and food stamps . How soft drinks and junk food should be a luxury not covered. 
Well I had a hunch as to why those things are available to SNAP users. Here we go.
Pepsi Co, Corn Manufacturers of America, various grocery chains etc. They have all lobbied our lovely government. So that these things are available on SNAP cards. That is just lovely. 
Just like things I read on The First Ladie's Let's Move Campaign. She only mentioned food in the first few speeches. If that. Seems some big food corporations got a little angry. Sending out their lobbyist to attack. See the blame goes two ways. Yes people should not be buying crap left and right on Fed money. At the same time if the gov was serious. They would not let junk food lobbyist dictate to be covered on SNAP. They would not get angry when a health and fitness education program is started, and say "don't mention us". This is a shame.