Rights holders maintain control over where their content can be played. Hulu has to get permission for where a show can be played. There was a great post on Google+ a while back by someone well known... can't remember who that said exactly this: DRM is about control over hardware makers.

EDIT: Ah, found it, Ian Hickson: https://plus.google.com/107429617152575897589/posts/iPmatxBY...

Isn't that true of Netflix as well? Why is Netflix seemingly able to negotiate so much better than Hulu?

Aside from their own projects, I don't think Netflix gets episodes from the current seasons of popular TV shows the way Hulu does.

Because Netflix doesn't have episodes that aired the day before.

The most frustrating thing for me with Hulu Plus is that even when you're paying for it, it still shows you commercials. So my solution was to get Chromecast and just stream normal Hulu via a Chrome tab. At least that way I'm not paying them to watch commercials. . .

You mean, like cable TV? Hulu Plus is payment for access to a back catalog, like expanding the video-on-demand library of your TV service. It's not payment for eliminating commercials, and they never advertise it as one.