I feel like the more obvious explanation is that older developers already know the languages young developers want to learn. JavaScript, C++, Java and Python ar

I feel like the more obvious explanation is that older developers already know the languages young developers want to learn. JavaScript, C++, Java and Python are widely used and knowing them has a much higher return than Go or Kotlin as first or second programming languages. If you have been a developer for 10+ years there's a good chance that you either know these "older" languages or you know that you don't need/want to learn them.