Plastic Houses

Before coming to NZ I was warned by our Consulate not to come cos f . e. people live here in plastic houses. I did not believe but here it is all of plastic, wood and low or without quality (with extremely high prices). The risk of fire is not small and every day it happens. But who has got the idea to built houses in that way?
Of course there are as well extremely luxurious houses, but it is very small percentage and it is about very rich people. Or, maybe I have to change my glasses.