Because Android is Kotlin's selling platform, on the JVM it will be as relevant as Beanshell, jtcl, jython, clojure, scala, and many other guest languages.
Guest languages relevance always fades away as the platform language improves and the FFI gets out of touch with that old version of the language.
C18 on UNIX vs C++, JavaScript vs Typescript (see private members), and when time comes inline classes/reiffed generics/SIMD types vs being able to target both Android and JVM on Kotlin's case.
Young men are always trying to count progress as the reiteration of what has already come before them.
In reality, while the differences are minor, they are the same thing. Time fades away, and market dynamics operate the same as they did 10,20..100 years ago.
The hubris is in using absolute statements ("platform languages always win") instead of being a little bit more humble with their projections. Old men should know better that history rarely unfolds as expected.
Indeed, bare my words, in about 10 years time, Kotlin will only be a thing on Android, assuming Fuchsia wasn't brought into the market as Android's successor.
Guest languages relevance always fades away as the platform language improves and the FFI gets out of touch with that old version of the language.
C18 on UNIX vs C++, JavaScript vs Typescript (see private members), and when time comes inline classes/reiffed generics/SIMD types vs being able to target both Android and JVM on Kotlin's case.