There's still a market, but Apple's not interested in being a bit player in it. HP, Dell, and SuperMicro utterly own the server space. Taking those companies head-on with a single one-size-fits-all server is never going to work, and Apple wasn't prepared to build out a complete server line.

The "Server" software they have is for small businesses and is pretty good for 10-20 users, but beyond that you'd probably use Google Apps, Microsoft Exchange or something more serious. It's a nice thing to have, but it can't compete at an enterprise level.