All of the above reasons are valid, including an addl one. Your 1 coupon direct flight does not contain taxes fro ORD as an addl segment, that if u took 2 flights, UA would also now be liable for (XF/PFC).

As to the "getting punched"...didn't hear this one, but saying it would be in the news is BS. I know of numerous GA that have been assaulted by customers over the years, and none of them made the news. UA doesn't call the press to say an agent was assaulted and battered, and most of the people doing the assaulting don't call the press either.