Business controls it. Research has contributed little, despite a huge flow of papers on caches, proxies, server architectures, etc. A huge amount of work, but if you don't honor the standards you're marginalized. At another level, instruction architectures, buses, etc. have the same influence. With so much externally imposed structure, there's little slop left for novelty.
Academia is a casualty.
Today's graduating PhDs use Unix, X, Emacs, and Tex. That's their world. It's often the only computing world they've ever used for technical work. Twenty years ago, a student would have been exposed to a wide variety of operating systems, all with good and bad points. New employees in our lab now bring their world with them, or expect it to be there when they arrive.