This question already has an answer here:
Is it the airport security at the country you flying from? I highly doubt it because I have been to countries where it's so corrupted that you buy the airport officials for the price of a dinner.
Is it the aircrew' responsibility? Again I don't think they care much - unless there is severe punishments - in corrupted third world countries.
I have been personally in a situation when an officer at a certain airport insisted on examining my British passport before he allowed me to move to the gate because I refused to slip him a $100 note. I was travelling to the UK yet I have another passport which is valid and it is issued by the country I was flying from, which means he had no reason whatsoever - nor I think he cared - to examine my British passport to check if it's valid.
Edit to summarize it, I want to expose as little as possible of information about my dual nationality. For that I need to know whom I am obligated to show my passport(s)