The commerce commission sent out letters to all the ISPs advising them to stop advertising 1gbit speeds because consumers kept complaining and they were going to start investigating. 


They said that the technical offering of gigabit did not meet the consumer 'real world' expectations and they strongly advised all ISPs to stop offering it. 


However some do use the point-to-point fiber offerings that can indeed meet 1gbit so they will still advertise it - but you will notice the price is business grade, not residential.