How come all the american sports networks pass up on so many good fights?

I guess they don't think they can get the advertising dollars necessary to make it worthwhile for them. CBS took a chance and tried putting Strikeforce on a while back, not sure how well it did for them. It's not on anymore though, so I'm guessing not that well. It's a shame, we're missing out on a lot of great bouts. Thank God for live streams.