I&#x27;ve noticed that programmers tend to become more interested in functional programming over the duration of their careers. I think this is because, as a paradigm, FP solves problems that only experienced programmers realize they have. I&#x27;m not sure what the age distribution of working programmers is, but I bet the median is in the low 30&#x27;s at this point, which is when you start being interested in FP in a real way.<p>The other side of the coin is that there is tremendous &quot;practical momentum&quot; in software that is collected in the mass of code written in non-FP ways. Experienced programmers are usually expected to fix the symptoms, not cure the disease. Clever people might slip in some functional ideas here and there, but you&#x27;re almost always better off learning the nuts-and-bolts of integrating Lucene with your Jetty app than you are learning Clojure.