Lath & Plaster is still pretty common, they were usually built without insulation so retrofitting the knob & tube was actually pretty simple to do from the attic.

Bathrooms have usually been gutted though, if for nothing else than the common designs had windows in the bath/shower and pretty much guaranteed water damage in the wall.

a significant fraction of the houses in major cities in the northwest, particularly seattle, are these sears homes. there are entire blocks of them, built around 1920 by developers plotting out whole neighborhoods.

many have extensive renovations, others are essentially standing as-built. typically they are worth millions, but that's more about geography and zoning than the construction itself.

i have lived in a few, all with the original plaster, and a mix of original plumbing/electrical. generally i would say even the mostly-original ones were are some of the nicest places i've ever lived, but that's not saying much.

there is definitely a survivorship bias, but the ones still standing seem to have weathered the moisture well. much of the ~70/80s era construction i have seen seems to have fared worse, and the new construction i've seen is downright laughable.

As a person who grew up and still lives in and around Seattle, I agree with everything you've said. Only thing I would mention though is:

>typically they are worth millions

That might be just a more generality of single family homes in the Seattle area than a nod to their craftsmanship.

I think you’d be entirely surprised to discover how many have NOT been gutted. Most houses built in thy era still standing probably have original piping or wiring somewhere.