Cosmetic stuff, square footage requirements, height requirements, parking requirements. Basic structural engineering, fire safety, etc. requirements of course would stay but if local code is more stringent than national you might take a look at it (e.g. things like a local code requiring copper pipes when PVC is acceptable and much cheaper).
Unless there's a need to build to a higher standard with longer maintenance periods, so that housing stock can have a longer life. Houses exist for decades, better to build for that without needing maintenance but perhaps costing more initially.
Developers will always attempt to skimp on quality to save/make more money. Even people building their own home will sometimes try to avoid compliance. That's why the regulations are there.
GP obviously meant PEX, which is another plastic. (For people not familiar with modern plumbing: PEX is used for supply; PVC is used for drainage to the sewer.)
Maybe that’s what they meant, but PVC is also used for water distribution, cold water supply, and sprinkler piping (obviously all cold water but still pressurized supply applications), so it’s not at all clear that when they said PVC they meant PEX. CPVC is rated for domestic hot water supply, so they could have meant that as well. I’d say PEX was an underdog rather than the obvious alternative meaning.
