If you watch C-Span, hook up your PC or Mac via HDMI to your TV and sign in with your DirecTV account on the C-Span website and that way you can watch it in HD. You get to watch C-Span 3 on it as well. That's what I do. They also have C-Span Radio on it. You might as well make a C-Span account as well if you want.
My local cable company has 3 CSPAN's in HD, as well as Nasa, a local college bulletin board and PCN (Pennsylvania Cable Network). See, bandwidth can easily be wasted on that stuff by a local mom and pop cable company, why couldn't it be done by a massive corporation who has 50,000 times more resources?
True, I feel the same way. But for right now it's your only option to watch these channels in HD on your TV as well as watch C-Span 3 unless you switch to cable or maybe add cable on top of your DirecTV subscription.