By comparison, at Berkeley they recreate 61C Machine Structures every few years. Out goes the unimportant, in comes the new.
Lexing and parsing isn't even a vanishingly small part of the job. It's usually someone else's job. Someone who works on LLVM code generation for the XYZ processor is the wrong person to keep the Clang front end up to date with the latest C++ committee's standard iteration.
They should push DFAs and grammars into theory classes. That said, I do like the 2nd edition of the Dragon book, particularly the later chapters.