Food-stamp recipients and folks on social security are completely different classes of citizen. Firstly, we expect the food-stamp recipient to eventually get off of them and start providing for themselves. The social security recipient has paid into the system their entire life, and they are now entitled - by virtue of having lived long enough and paid enough in - to start withdrawing the money they've been coerced into depositing.
Interestingly enough, most economic studies of social security show that putting the same money into a low-risk index fund would've netted more gains, plus that money would've been available to the person with far fewer 'strings attached' (vis a vis able to be withdrawn earlier if desired, descendants/spouses able to withdraw in case of untimely demise, etc). Coerced gov't meddling, again, has proven to be the more-painful economic road to go down, as opposed to letting individuals choose what to do with what they've earned.