The idea is that if something would have been a compile-time error (ex: using a method that doesn’t exist), but you don’t see that compile error because you don’t have a compiler, the error is still there. It’s just that you won’t see it until the associated code happens to run. Essentially the compiler can catch whole classes of bugs early on. Just because it’s annoying to be told your code has bugs doesn’t make that better than having bugs and just not being told.