This works for ISO standards in many areas. In many environments there are requirements to be standards-compliant. Buying the standard is a prove of compliance

This works for ISO standards in many areas. In many environments there are requirements to be standards-compliant. Buying the standard is a prove of compliance. (Turn it around: "you didn't even obtain the standard! How could your product be compliant?") This is of course mostly relevant for engineering. Less so in IT, but even IT standards compliance is sometimes part of government contracts. At least for language compilers. And yes, nobody will be able to verify the compliance, but commercial vendors document how well they comply to the standard and that limits the liability.