F# is very popular, for a functional programming language. In 2014 it was the most popular functional programming language on the Tiobe index, excluding SQL (in the latest index it has dropped below Scala, Scheme and Prolog). However, functional programming languages are not highly popular. Most programmers never learn any functional programming languages, choosing instead to learn one of C#, Java, C++, Javascript an…
Now if you're talking generic functions and higher order functions, maybe. But those are rarely needed, as you rather want a tuned specific version instead - or a template.