Can only assume NZ rugby and cricket have looked into it and the sums from Sky are massive. Sky's whole business pretty much relies on rugby so they wouldn't let it go easily. They could cope with a few grumbles over losing EPL and PGA golf but doubt they'd survive losing rugby. Be interesting to see if they make a competitive bid for EPL when it's up for bidding again next year.
We seem to be moving to the point where everything is going to come from a different provider and eventually you may end up paying the same or even more than a Sky subscription for TV, sport etc.