Why is there no machine-processable language of languages?

Like a KR or some system that could read BNF or whatever and translate directly into another level, like operations defined by the operating system or something.

Why can't we describe a language declaratively and semantically so that its low level details wouldn't have to be specified manually and so that it could be related to other languages and reasoning could be done about its effects?

The lowest levels of the system would probably have to be described as part of the same representation system.