Halliday & Matthiessen (2014: 417):
This also explains something that is often presented as an arbitrary rule of English, but is in fact anything but arbitrary: that if the Goal is a pronoun it almost always occurs within the phrasal verb (they called it off rather than they called off it). This is part of the same story; a pronoun is hardly ever newsworthy, since it refers to something that has gone before, so if the Goal is a pronoun it is virtually certain that the Process will be under focus. (But not quite; the pronoun may be contrastive, and if so it can come finally, e.g. they rang up me, but apparently nobody else.)