After I complete a candidates licence issue test, and providing they pass I have a discussion along the following lines. Often raise the point during training as well. Not always in one hit but the general gist is there throughout (I think).
I mention that the ability of just being able to drive the aircraft wasn't really in doubt or they wouldn't have been recommended in the first place! But I make it known that the only real change as a result of the day's effort is that now some poor, innocent victim is going to place his/her life completely in the graduate's hands while they go out and teach themselves.
Also that the average pax. has absolutely no idea of what is safe & what is not; what should be done or not; can't even distinguish between what looks dangerous - but isn't, and what looks safe - and isn't; that they implicitly, and wrongly, believe that you the pilot know 'everything' about flying & can do anything that they ask - they just have to 'persuade' you if you're hesitant.
I also discuss accident rates & peaks vs. experience. I always try to emphasise that they are in one of the highest risk categories, akin to the average 17 yo with a brand new drivers licence and their training was one of the safest periods in which they will fly. I realise this depends on exactly which numbers are used, but they are, or will be shortly, in a higher risk group.
I always finish with saying they should enjoy the beginning of a lifetime of learning & other wonderful experiences courtesy of aviation.
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Don't mess with the red switches.