Fair enough, but the subject comes up very frequently on these boards, and is also media-driven, at least on this side of the Atlantic.
I would never upgrade anyone just because of their position. I believe most heads of state would travel at the front anyway, not least for security reasons. Members of Parliament in the UK generally travel in Business anyway, certainly on long-haul. I agree they're hard-faced enough to ask - they wouldn't get to be MPs otherwise!
There are sometimes comments by a PNR which may include SFU - suitable for upgrade. This is a subtle way of saying that, all other things being equal, they should be upgraded. There may be many reasons for this though.