What else would they use if they didnt use the E-Jets?
The 737's are too big for a new comer into the NZ market and wouldnt be profitable. And cant get into and out of alot of airports in NZ where as the E-jets can.
If DJ really want to suceed they need to take NZ head on the monoply routes which isnt the triangle its the regional routes where people would prefer to drive because it costs so bloody much! The triangle is profitable but there are other airports in NZ which can make money.