> but they are so pervasive that everyone knows how to use them.
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.
I've a QR app because I need advanced options, but just tested that my stock camera app when presented a barcode or a QR read them without any action. It offers to open the link in the browser, to connect to the wifi or to search the numbers of the barcode.
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.
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.