The kind of programmer who don't check (or think through so that they can't fail) their map lookups is also the kind of programmer who don't bother with const. What a non-const unchecked map lookup gives you is a default-constructed value that has just been inserted for the only reason that operator[] returns a reference, which must "point" to something. That's bad and can be confusing, but it doesn't crash.

I see that problem much more often than crashes due to unchecked map lookups in production, which are very rare for me. Less than once a year.