Because the market demands it?
The market is changing. I'm sure people didn't understand cars when horses were perfectly good solutions for the last 1900 years. And at first, those who adopted automobiles did it not because the automobile was superior, but because they knew the potential was superior - and that the potential would never be reached if we said, "eh, horses are as good as it gets, why bother struggling with anything else when we already have something we know."
Seriously. Tablets aren't a fad. I know you and a handful of other Tech Republic users have made this claim at several points over the last several years. That touch is novel but doesn't really add any improvement. The growth of touch-driven devices argues against that claim. There is something substantial to this way of interacting with our PCs. It isn't just that it is FUN, it is more natural, more intuitive, more powerful, in too many areas. It can be quicker. It can be easier. Not just on a phone, and not just on a tablet, but on any device we interact with. It makes sense in cars. It makes sense on ATMs, it makes sense in a bunch of usage scenarios - including the desktop... maybe not as the desktop is laid out today - but the original automobiles were literally a horseless carriage. That carriage design wasn't ideal for an automobile. That didn't mean the carriage was superior, it meant it was actually inferior and had to evolve to deliver the improvements of automotive transportation.
Likewise, this tired old PC interface that we struggle with today - is about to have to redesign itself from the hardware to the UI, in order to be a better platform for productivity and entertainment tomorrow.
