To read about large transport aircraft taking off without flaps, for example, is mind boggling.
By George, I think the above problem is due to pilots treating checklists as a "to do" list and not a checklist that the function has been done. Most of the crashes due to failure to set flaps seem to have been due to the checklist being interrupted by an external event, such as ATC or something similar which can only occur where it is being used as a "to do" list.
If the checklist is run as a confirmation that the action has been performed there is less chance of the action being overlooked, although to be fair, there is still the risk that the action has not been properly checked. That was the case with a CRJ crash in the US where the flaps were set to the incorrect setting.