It sounds like you've always lived in relatively new/high end houses then.

Older houses might have a dedicated 240 plug for the dryer and the stove if they're not natural gass, but for everything else there are plenty of homes full of ungrounded 10 amp 120v circuits.

My current house was built in '82. Is that a new house? That's 41 years old at this point. Its a pretty average single family suburban build for the time, not anything especially fancy even for its day. Loads of houses we looked at in the area were built in the 70s and 60s and often had electric 240V appliances in the kitchen. That's about 60 years old, is that a new? A single car garage 1500sqft 3bdr house in a suburb sound like a high end house?

And yeah, my house is full of 120V circuits, but once again the house has 240V at the panel and could run 240V anywhere in the house if needed. As you pointed out, they probably do have a 240V plug for the dryer, ergo they've got 240V service at the property, so they could wire the kitchen if there's no wiring already. Once again, practically nobody has only 120V service at their home.

Yeah the only situation I can think of only 120v being available in a house is if it is a separate unit running off a 120v sub panel from the main building. The other option would be some off grid setups for like a tiny home might only run 120v. That is mostly because anything that would require 240v would be too power hungry to run off of the solar system.

That would be by choice, though. My mom's 110 year old house still has some circuits with cloth wiring. But it has a number of new (40-50 year old) circuits that are normal, grounded 5-15 120V. And the kitchen, basement, and garage have 240V receptacles. This is pretty much the same setup as any modern house.