my theory was that it seems to work for Australia (and also perhaps America). To counter the popularity of sport on tv as well as to compete with other forms of entertainment, you need high quality facilities. NZs model of self sustaining stadiums that can barely keep up with maintaining itself, while charging it's tenants through the roof to get the revenue to do so is likely to result in declining attendances, and sports teams going broke while having to charge higher ticket prices to recoup costs.
The counter argument to that is that we don't always have the population to justify the expenditure. Take Dunedins Forsyth Barr stadium as an example