i know the easy answer is just "capitalism" but as someone who has spent decades staring it in the face... it's because the point of philanthropy, much like "international development aid" is to get that money right back into dominant capital formations. food deserts and underdevelopment funnel SNAP aid dollars overwhelmingly into the pockets of giant industrial food and agribusiness conglomerates like [JBS, ADM, etc] these firms sit in a vertically integrated middle, externalize the risk and environmental degradation of industrial agriculture onto farming communities upstream and the poor health outcomes of their products to the consumers and their communities down stream while benefiting from the big pool of government subsidies that reduce the market price they pay for raw materials and benefit from the most unholy labor-protection carveouts for undocumented workers, prison labor, etc. they literally get us coming, going, twice in the middle, and they evade taxes the whole way.

some states have gotten wise to watching this here-and-gone pass through of billions of dollars and make moves to capture that money by offering to match federal SNAP with state money to buy products from in-state agricultural producers, to essentially 2-3x the benefits of those receiving SNAP, but they are usually nibbling around the edges and the infrastructure/investment to process all that b.s. has to be built out to make it work for broke people just trying to feed their families. and if it did a real dent to the current scheme, the bigs would find a way to blow it up. not to mention, they probably wouldn't be able to afford the match if it got big enough, because states can't print their own money.

its the same with international development. every dollar spent comes right back, usually with a bit added on top and the country that received the aid is usually sicker, more polluted, has some sovereign debt, and now is made to feel they owe the US a favor, diplomatically.