The NRL is also the premier rugby league competition in the world, whereas the A League faces a massive cultural cringe not just from the general public but from a lot of local football fans too. Eurosnobs are everywhere. Funnily enough in my experience actual Europeans who move here don't have snobbery over the A League, it's kiwis who do.
Anyway, breaking down that barrier would help I think. Not sure how though - the attitude starts with the media I think. Maybe if A League games were on TV One for instance, then One News would have a vested interest in being more positive about the comp in general and the Nix in particular.