Well on my type (A320) the only checklist that is "self-responded" is the After Landing Checklist (and this is also depending on the operator - some do it as a challenge-response checklist while other do it "self-responded"), which is deemed to be not very critical (the worst case would probably be forgetting to switch off the weather radar but with engines shutdown it will be automatically shutdown anyway independent of switch position - otherwise its just the embarrassment of arriving on stand with Spoilers/Flaps still out). There are some items that are considered more critical that require and answer from both crew members, but the PM will wait for the PFs answer before replying (f.e. PM: "cockpit preparation" PF (verifies the item): "completed" PM (verifies the item as well: "completed"). I agree with you that answering your own challenge is a practice that is error-prone.