I'll have you know that I assembled my computer five years ago for less than the cost of a PS3 and it's still perfectly capable of running recently-released games.
The only thing I've had to buy for it in those five years is a replacement power supply - which the local computer repair shop owner sold me for half its listed price on Newegg, and tossed in a free copy of COD4 with the condition that I show up at a LAN party the following weekend.
I probably should replace this thing at some point. I don't see how it can be considered any more of a drawback, though, than upgrading from one generation of a console to the next. In fact, I'd say it's more of a drawback on the consoles' side. It's not absolutely necessary to upgrade a PC in order to play new games, and a new PC will be capable of running every game that you had for your old PC.