Even my least tech savvy friends understand that their wifi password is like a traditional front door key: anyone with a copy can unlock the door. I'd call that very unsurprising to most people.

The idea that more sophisticated authentication is possible to prevent password sharing would be a surprise to most laypeople I know.

Also home internet is increasingly coming with smart routers that will alert you to new devices on the network. Tech savvy people are the only ones who BYOD.