The issue was people were not using them, why spend money on something most people are not using.
The problem is that around the same time that Dish stopped including OTA tuners in new receivers, Dish also started having more and more frequent contract disputes with local channels, to the point where it got absurdly annoying. Most markets were affected by at least one of those disputes (to make a vast understatement). More importantly, every
major market was affected by at least one of these major local disputes, meaning that most
people were affected. So, just when Dish customers needed the OTA tuners the most, and Dish was actively pushing those customers toward using OTA, that is when Dish made it less convenient to get OTA integrated into the receiver.
If the OTA tuner had been built-in, then there would have been nothing that Dish needed to ship to the customer. Dish could have still offered the free mudflap antennas as a courtesy. However, Dish also could have just as easily told these customers to go to the nearest big box store to buy a cheap one.
Instead of spending the money on having the OTA tuner built-in (so customers could be more easily prepared in advance of a dispute) Dish chose to spend money on shipping out OTA adapters and even rolling trucks for installers to add them in many cases. In some of these cases, the dispute was so short that by the time the customer received the OTA adapter, the dispute was already over. So, the customer really saw no benefit from the OTA adapter at all, so why keep it hooked up and actually use it? Remember, at that time customers did not yet have the option of dropping the satellite locals from their basic package to save money.
All DISH would have to do is add the Sling tv app to its apps and people could do the rest like I already posted. I know if they get a hopper plus with a browser to add what you want , you could add the app there and this would accomplish what I am saying.
Unless of course you are using a Wally, or a Hopper 1, or a Hopper Duo, or a ViP receiver...