If you custom build a gaming PC and you put 1500 into the PC (WAY more money then you need to build a decent PC) then I can guarantee you it will last longer then year before you "need" to upgrade it. That said PC gaming is still more expensive then the consoles and its very intimidating for someone who doesn't know much about PC hardware.
Factor in that low install base with the fact that PC gamers would be much less likely to buy he same PC sports franchise every year because of the great user created mods that often appear for sports games to upgrade and update them. It then becomes pretty easy to see why companies would be reluctant to put out new sports games on the platform.