i really dont understand what the big deal is about the billing order of artists? Does it really matter? No, it doesnt. the fact that the band is playing is all that matters. Put SPM on the 2nd line, put him on the first, we all know how good he is and how amazing the show will be. No point in debating spots on the bill. IMO
It matters to me, because I have a bet going with Phi that Mumford will be top 3.
Also it matters in terms of what slot/stage an act is playing. This matters to the overall experience. Take for example if in 2014 MMJ is billed 3rd. This means they will headline the What, which means a bigger deal and a bigger show than if they just subheadlined.
Works on a smaller scale as well. UM fans would be stoked to see them graduate from a tent to Which. The band would be aware of said "promotion" and thus be inclined to play a special show.
Well of course it will matter if you place bets on who is where on the list. As far as your other point, I understand what you are saying. But shouldn't every band try and put on a special show no matter what stage/tent/time slot they are playing on? Is being at Bonnaroo not a good enough reason to play a special show? Im sure that it happens but I find it to be very naive for a band/artist to say, "well we didnt get bumped up to a stage this year and our time slot isnt what we deserve, so we're just gonna get out there and go through the motions."