The reason behind it is simpler than many people seem to realize.
Sony stuck by their gun as the have been hell bent on pushing gaming on the same curve they have always been doing, at the same time, all other manufacturers were busy trying too hard to find some undiscovered goldmines all for themselves.
Nintendo thought they had the next big thing with the tablet/traditional controller mixture, whereas Microsoft thought their gain would substantially increase if they merge gaming with the more common and traditional mediums. Sony was actually the only one who stayed on their normal path pushing and focusing the area in which most console gamers care about.
I firmly believe the massive success of Wii/DS and the subsequent rise of casual market from Facebook and Smartphones deluded a lot of top executives. Everyone seemed too focused on an easy cash-in from a new untapped market, they started focusing less and less on the better defined console gaming market. Sony, I believe is the only who has been consistent in their vision of delivering high-end games, which although sort of backfired during the early years of last generation, it has been one of the biggest factors on putting Sony where they are right now in the console market.
