I understand why standards can be open while their implementations can be closed. However, I have a problem understanding the inverse. For example, the C++ standard is commercial, yet some of its implementations (e.g. gcc and clang) are open source. I believe PDF is like this as well.
More generally, would a closed standard not prohibit its broad use, which is one of the objectives of a standard? In reality, who benefits from what, and why are closed standards used?
In fact the C++ standard isn’t actually closed (its source is on Github …). You confuse “closed” with “published commercially”.
That’s a difference that comes stems from the unfortunate fact that maintaining and publishing standards documents simply costs money, and organisations such as ISO want to get paid for doing (part of) this work.
The situation is very similar to patent offices, and even more so to publishing in research: almost all research is open – for about any definition of the word – yet the publications are more often than not hidden behind paywalls, because the publishing houses pursue a business model that is paid per view (in addition to some upfront fee paid by the researchers).
On a personal note, I believe that this is a perverse situation that is an ugly anachronistic hold-over from a time before Internet when publishing a manuscript actually cost money. I’ve got some more things to say on this topic but the moderators would censor them. 😉