Top 10 reasons:
10. He had trouble redeeming US miles on UA.
9. He has no US miles b/c he's burned them all.
8. Flying through PHL and the unnecessary baggage delays are just too annoying.
Ok, I'm tapped out at those. For the record, I didn't attend but I wasn't personally invited. And I have disabled the feature in Outlook that tells people if I've opened/read their emails...I don't like that.