And that's part of the trickery involved here. People say "look that one guy died in that house so we need to require stricter code here." They're not noticing the freezing homeless people that died because housing become $X dollars more expensive and they lost the musical chairs game. Sure the homeless guy wasn't going to buy a brand new house, but through the substitution effect across a wide swath of society eventually down the chain it does filter down to everyone ultimately affecting their access to housing.
The ability for voters, already homed, to just change up the codes on everyone while not having their own homes subjected creates a cruel moral hazard and socially bifurcating effect. The guy that gets in early comes in and gets his, then says fuck you, you have to play by different rules.
I'm not saying the houses should be torn down. I'm saying any updates should put situation where homeowner voters are subject to their own medicine. I don't think they'll choose to tear down the houses. No they might decide after all "hey good enough for me, good enough for you."
As for "can't build with X thing they did/didn't have before." Well you can update the codes to allow both the old and new method for something. That would satisfy conditions for both standing and new construction without uniform enforcement causing old houses to be demolished.
They're not about protecting property values for existing homeowners, and that's a truly bizarre, nonsensical interpretation.
Building codes are about making new construction safer, because the cheapest time to make new buildings safer is when they are built. And we built them to the latest safety standards because the modern code reflects new dangers which may not have been relevant when older buildings were built.
If you really can't get that, then it's clear that your issues with building codes are more about ideology than anything to do with reasoned thought.
It's not reasonable to build with GFCI outlets in the bathrooms in 1956. It's not reasonable to build without them in 2023.
Most places have a very limited enforcement appetite for existing construction. If it was safe and current when built, it's fine enough. Exceptions include adding smoke and carbon monoxide detectors --- but they're not that expensive to buy or install; and sometimes you can't get a home insured if it had certain electrical panels with poor safety records, and knob and tube wiring is sometimes frowned upon (but really, it's not that bad if it hasn't been altered; just a lot of houses where they added too much load on the existing knob and tube and overloaded wiring is never good). That doesn't mean you should build that way today. Somethings that were standard aren't even available anymore; nobody makes orangeburg pipe since the 1970s, so you've got to use something better.