Why would someone have Priority Pass
So, given the few large alliances, why do you think someone would have a Priority Pass. I can think of a few reasons, but am going somewhere with this, so bear with me...
1. Does not travel enough to have lounge access with the main alliance or airline flying out of home airport.
2. Has enough travel for lounge access with main alliance/airline, but not second or third one.
3. (Specific to BA) travels loads, but never earns club points because always takes lowest possible restricted fare. (Other airlines always let you earn somthing towards tier status.
4. Does not realize that in many countries Diners Club membership costs less and gives same or better access.
5. Company pays.
In any case, I was surprised that rankings of worlds best and worst airports by people who only fly an average of 17 flights per year would be taken seriously, as per the Priority Pass results. Surely you would get better information by surveying all the Gold/Black card holders of different airlines where you can be reasonably sure of 100+ flights annually.