I found out about those as a kid when we moved into a house that had them still, and when I asked my mom she got a kick out of getting to teach me something. Haha. She’d had those as a kid. And then when I worked for the telephone company, I found out there are a surprising amount of older homes that never had them updated

But it just never occured to me there would be regional variation in phone jacks like there is with electrical plugs.