For what it's worth, my compilers professor shared this complaint, and was vocal about it on the first day. He structured his class so that he gave us a (nearly) working compiler for a simple arithmetic language (with lex/yacc). Throughout the semester, we gradually added features to the language it compiled until it looked more like C. By giving us the BNF for the grammar in each assignment, expanding the given parser was trivial. It did mean that we were guided towards maintaining his pipeline stages instead of devising our own, but they changed more and more throughout the various projects. This also meant that poor design early on lead to a great deal of refactoring in later projects.