Sadly it's not an attitude, it's policy. You board, you lose your place in line on the UPG list. UA/AA actually come on board and get you. I don't know who's policy is better as I've seen people get upgraded while on the aircraft, not want it, and now they have to replace two people's seats as opposed to just the one. Personally, I would be hanging out in the gate area if I had a coach ticket and was right on the bubble.