Studio 60 had some great people attached and good critical reviews, which is probably why it held on for so long - and no one wants to piss off Aaron Sorkin. The US television biz is brutal and often unfair (I've had several of my favorites canceled before their time). More often than not, whether a show continues is based only on demographics - and thus advertising rates - which is why Buffy and Gossip Girls (low-rated overall) survive. Studio 60 lost viewers continually throughout its run despite its quality. It's the U.S. I guess - nothing we do makes much sense...
Sorry to go on, I have a friend in the business and I'm rather fascinated by it.
Love the icon ;)