A language is like the most flexible user interface possible - anything can be combined with anything else. Imagine how many edge cases, exceptions, quirks, etc

A language is like the most flexible user interface possible - anything can be combined with anything else. Imagine how many edge cases, exceptions, quirks, etc you would have to manage and have it still work. Sure you can limit your scope and say "for these constraints, the optimization will give 10x speed up", but in practice that won't cover many cases. For any optimization process to be worth it, it has to applicable in a wide range of situations (simplifying I know) while guaranteeing no ill side effects. Proving algorithms, especially ones that have to function in the real world, is very difficult.