As far as I know, generalization of parser-compiler is more for academic purpose ("language" theory, where deep truths about languages could be discovered). It

As far as I know, generalization of parser-compiler is more for academic purpose ("language" theory, where deep truths about languages could be discovered). It seems that too often, one needs to modify the code of the parser-compiler itself, and a generic parser-compiler is usually "expensive" code, then it is better to write one taylored for his/her needs.