I don’t have any actual data to back this up, but I think that’s probably just the nature of things with how Kotlin has positioned itself in the market. Kotlin is really just better syntax over the Java ecosystem for most of its users; companies using Kotlin in production are likely working in a JVM stack, so they need to know that you can work well within the JVM ecosystem (knowing the Java libraries, tools, frameworks, etc). To that end, The Java ecosystem is what these companies are looking for, not the Java source language. I’m sure many of these companies wouldn’t object to using Kotlin within their existing stack, if they don’t already