EWR764 hits the nail on the head.
i work in software sales. and what cracks me up is clients who say "i need a software that does EVERYTHING." i tell them to let me know when they find the unicorn solution because we have not see one yet.
same goes for UA. they can't make everyone happy. they need to allocate their resources to get the highest utilization they can. they clearly feel MSY is not the best utilization for that a/c. don't like it? fly NK or AA. there is no unicorn airline.