As a master plumber I have found over the past 40 years plastic piping systems are the most expensive systems to be placed in a building where the owner plans on keeping the home.
If I was to work for a get in and get out and never look back type of home builder and had non skilled employees then I would certainly pick plastic over a quality, non carcinogenic material such as cast iron.
Even Charlotte pipe the manufacturer of plastic and CI recommends CI for above ground drainage and waste and soil lines and plastic for venting.
Plastic piping needs proper supports BUT considering the caliper of installer found installing plastic in most cases they use band iron in lieu of clevis hangers which should be spaced much closer then required for CI piping.
I do suggest plastic piping for people with hearing problems as they will not notice the excessive noise and don't mind having a drain cleaning guy available as the short radius fittings do cause a lot more stoppages then a long sweep that is readily available in no hub cast iron.
Every NH CI joint in reality is a possible clean out.
You normally get what you pay for, an example an Americast / cast iron bath tub cost 3 times more then a steel tub thus for those builders interested in cheap as possible low bidder gets the job plastic piping and steel tubs is the way to go.
By the way FYI go on the internet and type in "Toxic plastic" and then ask yourself what are the real qualifications of the so called plumbers who want to install it in your home