A lot of the problem starts with unprofessional instructors who're too lazy to teach properly.
How many FI's go out every time with the stude and go through the pre-flight? The stages used to be 'You go out and do the checks and I'll be out in a minute' progressing to 'Start it up and I'll come out' as the stude progressed. Is it any different now? I doubt it.
And how often does a FI do a W&B with a student?
Once? Twice? And a PPL's expected to remember how to do it when nobody checks him except in the ground exams.