If recursive descent parsers are so trivial, why do we have so many DSLs to generate parsers? :P Also, a recursive descent parser isn't going to spit out an AS

If recursive descent parsers are so trivial, why do we have so many DSLs to generate parsers? :P Also, a recursive descent parser isn't going to spit out an AST that matches the needed NFA/DFA, so there's going to be a transformation step needed.