Perhaps the major reason is the fact that the competeing programs in Japan do not offer any great benefits over AP. Both major programs(JL NH)the points expire after a certain time. When flying to and from Japan on AC , I am usually upgraded(100% this year) using the certs or OP as the flights are usually full with package tourists with no status. The program suits me fine , and feel that I am treated fairly on most occasions. I have never had any problems using my points for air travel redemption as long as I can plan ahead. Many of my Japanese freinds in the know also use AP or UA or NW or AA prefer the North American programs as they offer more benefits than the home grown Japanese programs. My 2 yen worth.