Sadly I have no way of tracking that, because I would make the opposite bet. My guess is that 90+% of QR codes, that people aren't forced to scan somehow, are never used.
Lots of restaurants are forcing this. I stop going to them. I don't go to a coffee shop to spend 3-10 minutes futzing with phones instead of talking to the person I'm meeting.
Not really, anymore. Android permits you to take a picture of a QR code and use it's URI later by going to the saved picture and clicking "Lens" (which activates Google's ML to identify QR codes).