This makes perfect sense and I wouldn't be surprised if that was the reason. The other thing, at least with NBC Sports Chicago, is I bet viewership has gone down over the past couple of years across the board - not just because they lost the Cubs. When I first got Dish in 2009, then CSN Chicago was the channel that was on most of the time. I didn't rely on ESPN except for a show or two and then the exclusive games. But over the years, as cost-savings moves, they have removed their highlight show that was equivalent to SportsCenter that they would replay overnight. There is no more SportsNet Central, which was like a mini SportsCenter but just Chicago focused. There is no more "Sports Express" or whatever it was called, a 20 minute show on repeat just the Chicago highlights. Sports Talk Live, which is an hour of talking heads debating sports from a Chicago point of view, was just recently canceled. Over the last couple of years there has been a lot more poker shows, replays of games, outdoors programs, and paid programming.
Just checking today's schedule, there are 10 hours of paid programming out of 24 hours. Most weekdays is between 6-8 hours. It used to be 3 hours of paid programming in the 2-5am timeframe; today paid programming goes from 2-noon. It was never like 5 years ago.
I don't know what the FOX RSN's or Altitude has done, but the quality of the NBC Sports Chicago has decreased over the years. And with that, my viewership of it as I watched it less and less outside of the live games. I am guessing others have as well, and that lines up with Charlie's data.