I lived most of my early childhood (age 6-19) in a house built for us in 1953 and we had switched lighting outlets in every room but it was built to "GI Bill" standards in DC where that meant something. We even had a breaker panel and grounded Romex. (fiber jacket 16ga ground). One of my first electrical projects was helping my dad switching all of the receptacles from 1-15 to 5-15, using that 16ga grounding wire. They were even polite enough to leave enough pigtailed in the box to hook up the 5-15 although it wasn't the full 6".
Somebody at work gave him a couple boxes of them before they were really known by most people in the country. The Navy was supposed to evaluate them. We had 5-15s long before we had anything to plug in them
The house I grew up in, in Santa Ana, CA, sounds very similar, right down to the 16 AWG grounded romex (Actually it was a funky shimmery green sheathed "Paranite - Parasyn" Built in 1958, There were P&S 5-15 outlets in the bathrooms, laundry, kitchen and garage, using metal boxes and the "stove bolt". Everywhere else, the grounds were simply crimped together. I broke the crimps and added a pigtail and new crimp when I changed out all the 1-15s (and 2-15's which were at all the half hot locations in the bedrooms and living room.) to 5-15 Decora's. My grandmother thought she was highfalutin with her new 3 prong Decora outlets