You've gotten enough answers already that I'll mention only a couple of things I don't see mentioned yet.
First and (in my mind) foremost, procedural languages have benefited greatly from their degree of commonality. For one example, almost anybody who knows almost any of the mainstream procedural (or OO) languages to almost any degree can read most of the others reasonably well. I actively avoid working in Java, C#, Cobol, Fortran, or Basic (for just a few examples) but can read any of them reasonably well -- almost as well, in fact, as people who use them every day.
On the functional side, that's much less true. Just for example, I can write Scheme quite reasonably as well, but that's of little use in reading Ocaml or Haskell (for only a couple of examples). Even within a single family (e.g., Scheme vs., Common Lisp) familiarity with one doesn't seem to translate nearly as well to the other.
The claim that functional code is more readable tends to be true only under a narrow range of conditions. For people who are extremely familiar with the language, readability is indeed excellent -- but for everybody else, it's often next to nonexistent. Worse, while differences in procedural languages are largely of syntax and therefore relatively easily learned, differences in functional languages are often much more fundamental, so they require considerable study to really understand (e.g., knowing Lisp is of little help in understanding Monads).
The other major point is that the idea that functional programs are shorter than procedural ones is often based more on syntax than semantics. Programs written in Haskell (for one example) are often quite short, but its being functional is a rather small part of that. A great deal if it is simply that Haskell has a relatively terse syntax.
Few purely functional languages can compete well with APL for terse source code (though, in fairness, APL supports creating higher level functions as well, so that's not quite a large a difference as in some other cases). Contrariwise, Ada and C++ (for only a couple examples) can be quite competitive in terms of number of operations necessary to accomplish a given task, but the syntax is (at least usually) substantially more verbose.
