Someone pointed this out in response to a tweet regarding QR codes that they're sticking to timetables at bus stops that link to the temporary timetables they're running. I'd agree with you, a lot of older people aren't too clued up with QR codes, or as you say others won't have/use any mobile data. But it must have been seen as an aggressive tweet as the condescending reply was along the lines of 'lots of old people have smart phones'. That's ok then
My grandmother has a smart phone just so she can play solitaire, if she's waiting at the bus stop not knowing there's a temporary timetable a QR code will be completely lost on her, and I'm sure the majority of other elderly users.
No offence to anyone who considers themselves 'elderly' and fully understands the technology!