It's just the way they do things, every week they have a new promotional thing (usually something much less exciting like 40% off movie tickets or a $4 Little Caesar's).
I was really hoping the MLS deal would stay because I do want it but I don't really want to pay for it, and I did switch to T Mobile pretty recently. MLB.TV no longer important to me since I live in the Phillies' region, plus I get it for free as a partial season ticket holder to boot (which I will never use unless I'm bored and want to watch a Mets game, or maybe in September when there are playoff implications).
Still getting a good rate from them though, plus free Apple TV (sans MLS) and Netflix. Hulu also now available. And free airplane wifi though I think they have cut back on that benefit too.
Meanwhile, aren't MLB.TV games free during spring training, or at least last year's subs are still good?