Look at it this way, back in the '80s only a small section of the population had desktops, those that had them needed them. The the revolution came and desktops became ubiquitous, but the vast majority of people didn't really need a computer, so as the tablet revolution came those people began switching to tablets and the desktop is returning to just those that need a desktop.
Personally I have all three formats (a Mac Pro desktop, an iPhone 5 and a bunch of tablets, including an iPad Mini).