idk i've grown up around a family with various siblings, and my experience has generally been that doing much of anything with a baby, especially one that shits itself is often more work than it's worth.
maybe this shits uniquely american, but i can't recall anybody just changing their babies diaper in public. In public bathrooms sure (a car even? Though i don't consider that public), there's changing stations there, and it's to be expected, but certainly not just, in the middle of a park.