It seems to me that one of the necessary functions required by every organism in order to survive, is to have the means of providing food for itself and its offspring. What was the initial reasoning in starting a federal program to provide this function? What percentage of people who use these services are hungry? How many people who don't use the services are hungry? What percentage of people are perpetually using these services, compared to those who only use the services temporarily?
Governments that implement the type of programs you refer to typically believe that their are people they represent who are unable to meet their dietary requirements through their own means. Politicians supporting such policies often claim that increased domestic security for more people lead to more active job/community participation which raises additional tax revenues from the individuals as well as the businesses they frequent and society benefits as a whole.
In the United States in 2011 14.9% of all households were food-insecure for at least part of the year, meaning that eating patterns for at least one member of the household were disrupted at some point during the year due to financial restrictions according to the United States Department of Agriculture. Of those households, 57% percent participated in one or more of the food assistance programs that you highlighted in your question. For all participants in these programs the average monthly net income per household was $336.
SNAP benefits were received by 15.5% of Americans in September 2012 implying that some percentage of those were not food insecure, though it is impossible to tell what the food insecurity number would be if no one received assistance. The USDA also estimates that between 3-10% of people who are eligible for food stamps are not taking advantage of the program today.
The average length of SNAP participation for new recipients is 8-10 months. Despite this, there are a significant number of active recipients that have been on the program for extended periods of time. The USDA reports these two seemingly contradictory facts about participation lengths:
- Half of the individuals entering the program during the 1990s received benefits for eight months or less; nearly four out five left the program within two years (see figure below).
- Half of all participants in a typical month during the mid-1990s were in the midst of a spell (a period of continuous participation) that had lasted more than 4½ years.
A full 80% of all new participants leave the program within the first 2 years. The full report I was able to dig up is not the most recent analysis, but it can be found here.