This bothers me.
Not because I care about the fitness program itself... but rather because this is a prime example why the whole "games as service" mentality sucks. People paid good money for this stuff and it's going to end with them being locked out of content they paid to use. It's a disgusting cash grab is all this was.
Furthermore it also entrenches bad faith between customer and company. I mean if you bought the xbox fitness then get screwed over with it, are you going to want to support Xbox in their next endeavour? Probably not.
I'd also suggest that this has the side effect of making people at least consider piracy a bit more. I mean if you as the customer have the option of paying (say $50) for a piece of content but the whole time you're treated like a thief (constant checks to ensure you can actually use the content you paid for) and it can be take away from you... Or you can get it for free, be treated like a thief anyway and have the content as long as you want it... It's almost like why would you even really bother paying for it?