Too much fun to program in. Lisp makes it remarkably easy to extend the language into just what you want it to be...which means that Lisp programmers tend to spend most of their time extending the language into just what they want it to be rather than solving the problem. (Indeed, this is often touted as one of the benefits of Lisp...once you have a suitably well-adapted DSL, the problem solution follows naturally.)

Meanwhile, the Java or Go programmer is thinking "this is boring and ugly. Let me finish this problem as quickly as I can so I can go home." So they finish the problem as quickly as they can, and then it's done, and it ships. And people have an incentive to use it rather than tinker with it because nobody really wants to peek under the hood, and the people who do peek under the hood tend to be really dedicated and care a lot about the problem domain because why else would you put up with the language?