Re: Why have PCs failed to have useful hardware improvements over the past 3 years?
I'll tell you what I think happened - consoles.
The biggest driver for PC development prior to Xbox 360 and PS3 was gaming, faster drives, higher performance graphics cards, faster RAM, more memory. Then, after PCs had caught up and surpassed the consoles, no one cared any more, because EA and Ubisoft had bought everyone, and believed that PC piracy would destroy gaming, so didn't bother developing for PC any more. Made commercial sense for them, and they've been successful, so fair play.
However, as a result, the market for PC gaming came to a grinding halt, and with it, so did development. Now everyone just wants free throwaway gaming apps where they can buy smurfberries, and they're happy - the drive for better machines dwindled, and what is most appaling, is that the PS4 and XBone have barely raised the bar by an inch, and will probably be the last of the old-style gaming consoles.
It's a pity, because whilst gaming is seen by some as a frivolity, the arms race it spawned in the silicon development stakes has benefitted us immensely - for HPC, parallelisation, simulations, speed - everything. These advances haven't gone, but they're slowing (though in their place mobile computing is driving down power consumption and increasing performance, but it will be a while before it gets to where the mighty desktop once roamed.) Desktops are part of the old "multiple consumers, limited markets" world. Mobile is part of the new "limited consumers, multiple markets" world. The King is dead. Long live the King.