Loads of places just have very poor implementation.
A few weeks ago I was waiting at a counter to order like an idiot for 15 minutes while everyone ignored me until I realised other customers were just ordering with their phones. Just a simple sign saying "please order with your phone" would have done the trick.
Another place I couldn't figure out what time the kitchen actually opened. Like you could order but the kitchen wasn't open yet. They just assume you would know something so obvious but it's not obvious if you don't know.
Teach them the hard way: replace some of their QR codes to open porn sites
In Brazil, some places also accept payment and offer a QR code on the table to speed up some data input. Some miscreants replaced said QR so the payment would go to their accounts instead.
Had that at a restaurant recently. It took me to a scanned image of their menu that I had to zoom around on to see everything. And it was multiple pages of that crap. What the hell is the point of that? At least format it for phones if you're going to make people do that. And this was not some mom and pop business.
This was what made me push my mom to go out and get a smartphone to replace her old flip phone. (That, and the fact that she had no idea how to send or receive text messages, or check voice mail.)
I hate that crap. At least post it on the wall or something. Don't even get me started on people demanding a tip at places where you have to do everything yourself.
I hate this so much. There were 2 times where I forgot to bring my phone with me:
One of them, they literally had to go next door to FedEx to print me a menu because they didn't have a physical menu.
The other place, they just couldn't serve me because everything is done online. You scan your table QR, do all of your ordering on there, and pay on there too at the end of your meal.