That's true for HBO and Showtime as well. And you could throw all of cable in there - AMC, TNT, FX, etc - pretty soon you've eliminated everything on TV worth watching. Half of my queue is TV shows (some stuff like
Justified that I could have watched live but missed out on, but mostly premium cable shows), so that doesn't work for me.
It's far cheaper for me to pay under $1 for 3-4 DVDs for a full season than it would be to subscribe for a 3 month season for $20/month. That's $3 vs $60, kind of a no-brainer, huh?

So no wonder premium cable is angry at Netflix. I've been expecting them to crunch the numbers sooner or later. I just hope they continue to regard DVDs as irrelevant.