If something may or may not be there, that should be a clear part of its type that the compiler checks you handled (even if it's just you deciding to panic, because sometimes that's the right thing to do). Then there can be a type for just the thing, no hidden possibility of it not being there that you have to check for, and almost all code can be written for the type that is guaranteed to be there, with only a little code dealing with only possibly-there values.