It's worth remembering that the number 1 decider for when games are and aren't is travel availability and cost.
That heavily influences the double header games. Auckland teams can play each on a weeknight evening because they're a 30 minute drive apart. The other need significant travel times and hence are on Saturday/Labour day.
It's also a big reason why they don't stagger same day kick off times - just not enough flights going to get one team there earlier or one team home later.
Why they've not staggered the Northern/Auckland home games to various week.... yeah I can't answer that one.