I believe that imperative languages are more prevalent simply because that's what more people are used to. Neither functional programming nor the imperative programming model is more obscure or academic than the other. In fact, they are complements.
One poster said that imperative code is easier to understand than functional programming code. This is only true if the reader has already seen imperative code, especially if the prior examples are part of the same "family" (for example, C/C++, Perl, PHP and Java). I would not claim that it's true for any imperative language; take a comparison of Java and Forth, to make an extreme example.
To a layperson, all programming languages are indecipherable gibberish, except maybe the verbose languages such as Hypertalk and SQL. (Of note, SQL is a declarative and/or functional language and enjoys enormous popularity.)
If we had been initially trained on a Lisp-y or Haskell-y language from the start, we'd all think functional programming languages are perfectly normal.
