Sports that a mass audience wants to watch is expensive (hence the OP). And establishing a news/talk show brand that people would subscribe to Netflix to get wouldn't be easy (and is probably a very different thing than acting as the studio for scripted shows). [ADDED: And honestly some politically polarized crap would be far more likely to fit that bill than historical network news organizations, however relatively superficial they were in some ways.]

Remember Netflix' incentives are very different from a network. Netflix wants to acquire and retain subscribers which tends to favor stickier content rather than filling up a schedule with programming that people will tune into out of habit.

Put another way, the network business model is essentially a legacy model. I'm not sure why Netflix would want to recreate an uber-Network.

Why would they? There are tons of free options for live news. Also they do have talk shows like the one letterman did.