[ho_schi]

I see some valid points.

    1. A restaurant should   provide a menu printed on paper or a panel. Sometimes pictures are used.
    2. Verbal communication serves that purpose also well. And friendly manner.
    3. Some cameras don’t  display the read input properly. Input is always in error until it is validated. Here is user validation required.
    4. You don’t need to invent excuses like “my camera is broken, I forgot my phone, Bad eyesight…”.
    5. You don’t have to carry around a camera, a cellular access terminal and a computer (consider this as description of a smartphone) with you.
    6. The website can load arbitrary data with JavaScript and mine Bitcoin in a sandbox. It is not safe because it will drain the battery.
   

I like QR-Codes. They are analog and digital at same time, printed on paper and machine-readable and nobody ruined it with incompatibility. If possible the payload is printed as ASCII aside the codes.

PS: Similar. To provide a common base, prevent exclusion of unwanted customers and prevent against malicious data processing some jurisdictions require cash payment options.