"...And you, as a consumer of that method, need to check every time if the return value is Null. If you don’t – you (usually) get a Null pointer exception and your program crashes."
Can't this be handled by the language itself, by default?
Just throw exceptions if you need to, and handle those. Semantically, exceptions and special null values are the same - they let you know something went wrong. However, I think that null values are a syntactic oddity much like a vestigial limb now that we have exceptions.
I now see the advantages of the monad way.
Of course; most sane languages require an explicit annotation to say that an object can be null. If it's not that type, there is simply no way to create an object that is null.
(Haskell is an example of a langauge like this; no objects can be null. Maybe and Either build on top of this system to provide a well-defined approximation of null.)
The problem with this is that nobody has come up with a sensible universal default other than crashing in some form or another. I doubt there is one. Static typing is just an attempt at failing earlier (at compile time, not runtime).
An example of non-crashing null behaviour: embedded systems without virtual memory where 0x0 is a valid memory address. Dereferencing/jumping to 0x0 makes your code carry on as normal. Hilarity ensues.
If you had an OO language mandating a Missing version of every type you define, then you can guarantee that you will fail at compile time. This has a better granularity than requiring the programmer to catch exceptions. The compiler can tell you which methods you need to implement, and the IDE could even scaffold them for you!
In fact, if a type has a neutral element on the conceptual level (like 0 or the empty string or the /dev/null logger), then the null-object pattern is applicable and we can return NullObjects instead of null references, so null references are superfluous.
If the type has no conceptual neutral element, however, the null reference doesn't relate to a meaningful entity on the conceptual level, either. (Medusa cars which kill you if you try to read the license plate are an obvious exception)