Nobody is removing null because null itself is not the mistake. The mistake was to say like in Java that null is a valid value for every possible class under the sun. What Kotlin & cie are saying is that if your parameter is a RandomGenerator, null should not be allowed there because null is not a RandomGenerator. Null is null and that's it. If you search something in a map, your value will be of type "String?", that is "String | null" and that's completely fine, the compiler will assist you with that too.