UA can do what they want. They treat domestic elites so poorly that I won't fly them. I have no idea why a FF would bother with them. I know many say it is for certain routes, but connecting, especially when you're not dealing with ORD, is really not that bad.
"AC is the innovator in the world of de-bundling. Robert Milton has been on this kick for several years now. The lowest fare (called Tango) has not earned status miles for several years now (but you still earn miles flown)."
AC may be the leader, but they really are in a monopoly position. UA doesn't have such a luxury. The airline is already getting by on its legacy international routes. I don't think they would want to push their frequent travellers onto NW or CO more than they have already done. Domestic companies are more often allowing only the cheapest tickets so it isn't as if companies will want to pay more for employees so they can accrue miles.