The problem is that the busybodies are usually well-meaning neighbors, trying to protect your kid from what they think is mortal danger. So throwing a fit about it is not a good look, if you care about getting along with your neighbors. The stakes are also very high: if someone gets mad enough, they might well report you to CPS, which is terrifying, especially when local laws in many places in fact allow CPS to decide that you were in fact neglectful. A more effective course of action is to work toward getting your state to pass laws protecting children’s independence.
Well, thank god I don’t live in the US. I can just send my kid to the convenience store and everyone will comment on how great it is they’re already able to do it by themselves, and how they’re helping out.