The most common failure case I see for broken QR codes is it scans fine but it was created using some commercial link-bouncer service and they stopped paying the subscription fees so the redirect is dead.
Fixed that for you. If you are using free stuff that you google-searched, then you're the product.
It sadly requires a lot of vigilance not to fall for these "petty deceptions".
Because it makes the QR code simpler (less "pixels") and therefore more robust. Given the same physical size, scratches affect it less, and a phone can read it from further away. You want to avoid long links in QR codes whenever possible.
The other thing is analytics, of course. You can generate 10 different small QR codes that lead to the same long URL, to find out where they're getting scanned, so you know which locations are popular and worthwhile and which ones are not.
And maybe don't criticize restaurant owners for being technically incompetent? I'm sure they would find you just as incompetent at cooking at scale.
Most QR code menus are entirely managed by just one company that is effectively a monopoly. It's not the restaurant staff making these terrible, it's the digital services provider.
Interestingly enough, printed QR codes physically degrading as described in the article is actual bit rot, albeit a form often overlooked.