The grade 3 is an idiot.
Mags can be knocked or vibrate to a single mag. Most pilots with more than a few hours will have seen this happen.
Masters can also be knocked off/alternators left off etc. Again, most pilots will have experienced this first hand or second hand when they go to fire up a dead battery.
Many passengers release the sash to take photos, grab something from the back etc and need to be reminded, no different to flicking on the seat belt signs if you ask me.
I'm sure a few guys can attest to having a door/window pop open on touch down because someone fiddled with the door in flight or leaned against the latch etc. Hence, hatches.
I've not seen PUF checks taught to guys prior to flying a CSU/retract or cowl flaps. These checks are as needless as 737 circuits or always positioning for a strait in approach despite being outside 25degrees from centreline, but you can't convince some people.
As for the rest, common sense, not all 172's or PA28s look the same but the checklists should.