Only if you got a significant proportion of users (>50%) to engage in it would it be able to reveal exchanges which were insolvent or faking volumes, and that was never going to happen. If you can't get through to a newbie why leaving their coins on an exchange permanently is a terrible idea, then there is no way you are going to be able to convince them to take part in "proof of keys".
Yea this was exactly my point there needs to be greater awareness about it in order for proof of keys to be effective and actually act as test for exchanges. Personally I think even if 30% of the community were to withdraw their money simultaneously it would be more than enough for cracks to start showing up with regard to exchanges where solvency was an issue. ( the conundrum ofcourse however is that if the exchange was insolvent they would naturally use an excuse to deny any such mass withdrawal as was the case with hitbtc for instance. But even then at the very least this would mean prevention of further people depositing money into an exposed exchange.)
Quadriga ofcourse is not a great example here since despite being exposed a lot of people continued to deposit more money into It, but like you said some people will never learn. ( similar situation happened with bitkonect)
Much better to just teach everyone to take their coins off the damned exchange.
Yea always better to keep money of exchanges but i think the reason most newbies end up leaving their money on exchanges permanently is because it is for many the first fiat to crypto gateway and many subsequently never end up taking the time to learn how to use a private wallet.