But the same as why modern homes still do not have a low dc supply for charging all the small stuff and for led lighting it is because changes have a huge impact.
Frankly putting such stuff into your home was impractical with ever changing charging technology ever changing. Say you had 5V charging sockets, they sort of can charge modern phones but at very low speed and some phones will pull more current than PSU can safely supply. Placing some permanent installation which you need to replace every few years is not the smartest thing to do, not to say most of the charging sockets available today are totally outdated. For laptops it's even worse. With a lack of common standard, it would be nearly useless and prone to destroying devices.
Yep. It wouldn't add any value. You can still install mains sockets with USB charging ports (those sockets can easily be changed and are not very expensive) if you want it integrated in your wall. Or just use external chargers just like we do, that have the benefit of being usable anywhere.
USB-C PD probably will change that.
USB-C PD will keep being revised just like any other previous standards, so that if you made that part of home mains installations, that would become "obsolete" (at least in the sense of not being able to provide as much power as the more recent revisions, thus being unusable with some potential newer devices) over time anyway.
The reason mains AC has been the norm for a long time and still the norm is that it's the most reasonable common denominator for distributing electricity that can adapt to pretty much anything without requiring a constant stream of changes.
If it became suddenly *mandatory* to equip new homes with USB-C PD ports, then it would by nature make that planned obsolescence that would require updates every few years, while an AC installation can last for decades.
OTOH again, anyone who wants USB-C PD ports in some wall sockets can install them for a relatively reasonable cost, then it is their decision and their responsibility.
Like this:
https://www.amazon.co.uk/Double-Socket-Charging-Screwless-Design/dp/B09SVGDDK4these are available all over the place these days - and the above is dirt cheap, count around 40-50 pounds for one from a major brand.