Yeah but Wellington city only has 160,000, and as far as I can tell, public transport from outside the city on a Sunday is pretty average. Given our home form it's pretty understandable why people don't come from far and wide at 5pm on a Sunday night.
Free parking in the city on Sunday though - and the part of town that the stadium is in has plenty of parks available. Anyone that lives outside of Wellington itself is going to have a car.