Low income foodstamps and medicare

On low income, I go to free food/commodies, but those on food stamps and medicaid won’t go there; they get so much money from the government they don’t have to; and instead of buying the “good” food; yes they choose the most expensive cuts of meats/such, but nost often junk food. Why not limit the amount of junk food and beverages, and in exchange for what they get, they must volunteer someplace?