Used to work for one. Another time, I had a guy from marketing who moved over.
For some reason, I never did get along with them.
The number one reason to have an IT HEAD that is knowledgeable about IT is because when you have two or three possible solutions to a specific business concern, and three different "factions" trying to convince you that their plan is better, someone who knows IT will be able to ask the right questions to ensure that the system that will best fit into the overall company infrastructure (long-term) is chosen.
I have seen people (no name calling, but lawyer jokes accepted) sign off on doing a simple project and taking a "two-day" solution vs. a "two-week" solution.
The scenario was... boss wanted a GLOBAL implementation of a document management and sharing system (this was back in about 1994 before intranets were common).
Guy 1: "I can do this in two days" (using NFS mounted drives).
Guy 2 (me): "well, we have these considerations that we have to work around, but.... hmmm, give me an hour...."
Guy 2 (an hour later): "ok, on consideration, here are the problems that we have to overcome, it'll take us two weeks to be production ready, (using a brand new web-server technology OMG)".
Guy 1: I can do it in two days, no problem.
Boss: Ok, Guy 1, make it happen.
six-months later
Boss: Hey, guy 2, we're having problems with this system, you're good with that, can you help work this out?
Guy 1: Hmmm, that sounds like the problems I warned you of when you first asked about this project.
Boss: Oh, you did?
Guy 1: yeah, here's a copy of that memo I gave you.
Boss: Oh, yeah, guess you did, anyways, go help them fix the system, everything is out of control there.
Guy 1: You realize it's now going to take us another six months to build the solution, and then to migrate all this mess into it?
Boss: ouch, that long?
Guy 1: Aye
Now if the boss in this scenario had known IT rather than focusing on the "I can get it in two-days", then we would have saved literally 8-10 manmonths of FTE at the expense of 2-3 manweeks of work.
Is knowing your subject important? I think it is.