I'm pretty sure the reason Sunday Ticket has been on DirecTV is because it has to be on satellite per FCC cable rules.
There's a rule from the 1950s that prohibits importing out-of-market affiliates into a market via cable. If you get two affiliates from two different cities on cable, it's because you can pick up both over the air via antenna.
I discovered this because the Mets games were on WPIX and we got that channel in Rochester. But then WPIX became a WB affiliate. Rochester had it's own local WB affiliate, so cable had to drop WPIX. For a brief time, the WPIX Mets games would appear on a channel that was like home shopping the other 21 hours of the day. But that got ended pretty soon, too.
When every NCAA Tournament game was CBS regional coverage, they had the March Madness DirecTV package which let you pick from the four games going on. It wasn't available on cable either (which follows that rule). Now they have all the games spread out over CBS, TBS, TNT, Tru, so it isn't an issue.