It's a lot of reasons!! Parents don't make enough money, parents buy themselves stuff before they take care of their kids needs because they don't care, abuse, bullying & I'm sure many other reasons. My parents were more concerned with making sure they had plenty of beer before my sisters and I ate anything. I was raised on hot dogs and pork n beans. Didn't have my first steak until I had moved out at 17.
I don't believe that number is accurate ... and for those that do, an unknown number has to do with their parents' choices (EG; buying cigs/alcohol instead of food, having cable/internet, etc) ... then you have people who have children they can't afford ...
There are many reasons, before you get to the "it's society's fault" answer.
47 million in the US are on the government dole, unemployment insurance, disability insurance, food stamps and cash assistance. Of those, some register their actual families, but do not feed them, Some 'fall through the cracks', just don't 'fit the bill' of assistance, or welfare. Some are dopers or illigal in some way and do not want to risk exposure, some are illigal immigrants who are in better shape here than in their home country. Some -are- paid to get fed, but it is not enough, priced msy be high, some do not want to change in their -dignity- by searching through market throwaways or ask. All the reasons that you think of are there. Look into the government website, "USA.Gov" and find any and every department 'we' have and search out the details. It's "World excuses", and the 'Bad guys' who take $$ from others and do not care.
The statistic has been thrown into considerable dispute, because they derive from 61,000 interviews of food stamps (aka SNAP) recipients, then projected to a total population. This is like projecting the number of people infected by the flu, by interviewing flu patients in a hospital and extrapolating to the whole population. What can be said is that, of those receiving assistance, the major problem is fresh fruits and vegetables, rather than calories. Of those not receiving assistance (and there are a good number of illegals in this number), it is a problem of not encouraging illegal immigration. No country in the world gives as generous a package of public assistance to illegals as America.