You have to want a better streaming experience than Valve's Steam already offers for free (and you can buy a Windows Tablet for the same price, and Valve is expected to support Android and iOS soon). You can use whatever system and whatever video card you want to stream the game to and from - even go wired ethernet to get around the inevitable problems you get streaming games over wireless.
If you go Shield, the tablet price is just the beginning: you have to have a mid-range GeForce card purchased in at least the last 2 years ($120+ if you don't already have one), the controller + stand ($100), and of course a suitable dual-band router runs at least $70 (most people use the crap one that came with their internet install).
In all, you could be on the hook for anywhere from $400 all the way up to $600. That's getting DANGEROUSLY close to the same price as an entry-level gaming PC, so again the need just doesn't present itself there.