Interesting. Shows you why Citi has had so much reported trouble adding AA to their Thank You Rewards program.
Unless you value the benefits (free bag, priority boarding), there's no reason to have the UA card over the Reserve or Sapphire. And if you're elite, there's no reason to value those benefits.
What shouldn't be overlooked is that Chase is still buying the points when people transfer to United. Be curious if they pay a higher rate for transfer vs. miles earned on the UA card.
And an interesting tidbit I didn't realize: "United also gets a cut of the swipe fees merchants pay when customers use the [United-branded] cards."