Sam,
You hit it on the head. UP is combining and/or cancelling (annulling in Railroad terminology) trains all over the system. This not just applies to general merchandise trains, but double stack container trains as well. I can understand why, unless it is really important or hot freight like in your picture above, it really isn't worth paying a crew to run it unless they can haul enough cars to make it economically viable. So Remember,
Save a buck,
on the yellow duck!
Of course my favorite of all times is
C&A,
the only way!