Nope. I know people first-hand who don't. Hell, even I don't know how the average person does it. My own phone's camera app doesn't detect them so I had to find a random 3rd party app and trust that it's not stealing the info. In fact I'm not sure I've ever used the stock camera app on any phone to scan a QR code before. For some folks it might be "press Camera and scan", but for others it's way harder than it looks.
My guests doesn't ask for the WiFi pass, they see the QR hanging and ask "what is this QR for?", "It connects to my WiFi", and they immediately try it (succesfully) out of curiosity, "It's cool, how is it done?". The don't understand the magic behind, but don't need a guide to use it.
I think there must be some sort of crazy interference going on because I can literally be sitting right next to the router and 5ghz has about 5k of bandwidth available.
Me: Is it doing anything? What did you do?
Vistor: No. I pointed my phone at it like you said. Then I took a picture.
Me: What app are you using?
Visitor: The photo app I always use.
Me: Can you be more specific?
Visitor (showing where the icon is): That one. I always use it.
Me: That one sucks. Do you have any others?
Visitor: I don't know. There's photos in the Facebook app. Should I try that?
Me (grabs a piece of paper from the fridge, exasperated): Here. This is my wifi info. Use the 5ghz one. If that doesn't work, try the other one.
Vistor: Oh, ok, whatever. Thanks.