Because it isn't necessary for the future they envision. It's like including a DVD drive on a laptop: some people might use it now, but it's very clearly on th

Because it isn't necessary for the future they envision. It's like including a DVD drive on a laptop: some people might use it now, but it's very clearly on the way out. Apple generally make these decisions before it's very clear what direction the industry is heading. Their decision here is to position the Mac Pro as a tiny, powerful computing hub that has the bandwidth and controllers necessary to drive a crazy amount of professional hardware at high speed. This unifies their products relative to external accessories (if everything is Thunderbolt, you can plug your hardware into your laptop when required). It also lets them stay focused on making the best 'pro' computing hub they can build. (That it also happens to be quiet and small is a very nice plus.) Edit: That said, who knows whether this is the right direction for the pro industry.