I sure wish I had perfect willpower to avoid bad foods. But, alas, I am imperfect in that regard so I create a system that prevents bad foods from being in my house. The end result is that my behavior trends toward more perfect than had that system not be in place.

Moral philosophical discussions are fine and we can lament about the moral shortcomings of ourselves and others, but I think the systems argument is more pragmatic in creating real changes in behavior and outcomes.