They looked into this before and there were a number of issues.
1) Contracts with Broadcasters only allow one Sling Stream at a time.
Then redo the contracts or when they are up.
Again this is something Comcast, Charter along with YTTV and Hulu Live already provide.
2) Streaming anywhere, including inside your house is not always reliable. You could be watching TV on a DISH Anywhere connection in your house and then you kid starts downloading a big file... your picture can freeze get pixelated etc... they want you to have the same experience everytime.
While true, this is why I wrote
in the rooms that do not get much use, I can see the Hopper 3 on the main TV, which would not be affected by what you wrote.
Also, would not the wireless Joeys and the Hooper Plus have the same problem as what you wrote, yet Dish has no problem leasing them.
If they ever want to attract a customer like me ( and others I assume), this is what they need to do, make it more customer friendly regarding these fees.
I have written before, I have 11 rooms with TVs, I use one Full Time, one other only when I am on the Life Cycle outside in the morning watching the news.
The other rooms, never, the only time some were in use is when we moved to Florida and our kids came with us ( they both have their own homes know).
This Thanksgiving and XMAS, I will have a full house, YTTV allows me to add unlimited streams and to go back down to 3 after they leave, total cost will be about $20 extra (total) for that time period.
If I had all those boxes from Dish, extra, at least, $50 a month.
If Dish offer their channels via a streaming app at no charge ( plus one Hopper 3 for the main area) I guarantee I would be a subscriber, because I would have a service not dependent on the internet, I live in Hurricane Land now, so if Charter goes out for a extended period, I would still have TV.