Not to step on anyone's toes, I just don't feel that formal grammar theory is that important in practice. :^)

Well, it depends how formal you're talking about. I have to say that the standard you mention, recursive descent parsing + Pratt for expressions. actually requires you to understand what a formal language is - that it's a "thing" that can't (or shouldn't) be an object or a data structure but exists abstractly before any objects created by the program.

Moreover, the standard way of producing a recursive descend parser is to begin with your language in Chomsky normal form or some human understandable format and then convert to Greibach Normal form and that specification converts readily to your series of recursive functions. So all language transforms are useful to know (though you can skip steps if you have a good intuition of your language).