Two things: 1) It's not "trivial" -- it's actually a substantial amount of work, especially as the language evolves. How many parsers have you written? Do th

Two things: 1) It's not "trivial" -- it's actually a substantial amount of work, especially as the language evolves. How many parsers have you written? Do they have public APIs? Which public APIs to parsers have you used before? 2) It can actually constrain the evolution of the language. IIRC Python has had some non-trivial upgrades that "reinterpret" text with a different parse. If you have to provide parse tree compatibility in addition to text compatibility, that makes changing things harder. I've noticed that people who have taken a compiler class (often not in C) but haven't worked on "real world" parsers (nearly all written in C/C++) have a very idealized notion of how they behave. Parsers written in C are more often than not tightly coupled to both the lexer and compiler.