The question is, why should this be part of the language or standard library? This can easily be achieved by a library.

The Kotlin type system does help though/is essential to correctly implement Option types where other languages like C# can not.

The essential part is you can/should define an Option type with a non-null upper bound. Otherwise you would have a Some() that still might contain a null value. So the side affect of solving NPEs you speak of is only there if a language actually supports non-null upper bounds.