In which case, the need for the spec should be obvious from the onset. Nobody though that html would be used the way it was used today. But we now know the same

In which case, the need for the spec should be obvious from the onset. Nobody though that html would be used the way it was used today. But we now know the same things as they knew back then, meaning that we do not know nothing, we don't know what will be used and need interoperability. Also, specs means nothing if each implementation can and will do whatever they want (ie. Chrome vs Firefox vs Edge)