A brief stop-over by a sitting President to shake hands and say hello would have made a significant difference in terms of pleasing donors and bundlers, particularly if some of these donors were previously Obama supporters.
Obama's no show would be seen as a snub and would have a depressing effect on donations.
Makes one wonder if Obama sees the writing on the wall re: a Hillary loss.
Hillary probably told 0bama that the cost to get in was $50,000, and he declined to pay to play.