Not all games are available for PC, so depending on your taste in games, PC may not cover everything, regardless of how capable any hardware you build may be.
Although it's understandable for some if you spend well over $1000 on a PC (to say nothing of top end $2-3k builds) built primarily as a gaming platform that they would insist on playing more games on PC out of principle.
But if you have a capable PC, it is a much harder sell to continue playing multiplatform releases on a console considering console copies typically cost $10 more on release and will always play at a lower frame rate and limited resolution.
Personally, I have a hard time buying console ports for this reason unless they happen to be heavily discounted and I just don't care enough about the difference in visuals and performance. Often, I end up buying both console and the PC version later when it's discounted on Steam.
But despite what any PC gamer would have you believe, console gaming is still more convenient as there is a lot less to tinker with in terms of installations and settings, both hardware and software. Yes, there are installations and updates on consoles, but the process is generally one button press.
Also if you're used to gaming on a big screen HDTV, it is a lot less convenient to use it with a PC since the primary controller is mouse and keyboard. Even with a wireless set up, you still need a lap table or keyboard cart, or have to switch from keyboard/mouse to controller if you use a game pad for PC gaming. I haven't used the HTPC hooked up to my HDTV in months and prefer to use the one at my desk for gaming.
But currently the ideal way to game on PC is not on a big screen HDTV anyway, but on multiple monitors (at a computer desk unless you have a nice multi-monitor array stand), which simply isn't available on console.
Everyone has different tastes and preferences though. I think anyone who simply prefers the typical living room console experience would be less likely to convert to PC as their main gaming platform.