[kqr]

You'd be surprised how incompetent most adults are at what they do. I'm sure some less technical person assumed QR reading works the same way everywhere, tested it with their device and went "Yess it works! Ship it!"

I also sometimes see QR codes that are inverted. Not all readers detect them but many enough do that they end up in print.

[TonyTrapp]

That being said, the QR code readers most people have in their pockets already have to be able to deal with all sorts of problems (blurry pictures, dust on lens, and many more scenarios) that rounded corners are unlikely to have an affect on any of them.