You are right, a single box of cake mix once a year is fine. But between banning processed foods, or allowing everything, the former is far closer to the "just cake once a year" scenario. Allowing unlimited spend on junk food will in most cases lead to worse outcomes.
>SNAP's stated purpose is nutrition
SNAPS purpose is dual, and it was always also about ensuring american farmers had more demand, including for corn syrup. Horrifically, EBT being spent on soda is intentional.
If that bothers you, we can reduce corn subsidies without taking candy from literal children, or keeping poor parents from buying chips.