CO relies heavily on the fact that they have fortress hubs, and that dictates their philosophy. Their people need clean safe reliable transportation. Gordo-CO cared about winning customer loyalty since their brand was in the toilet from years of mismanagement. CO now thinks that their awards of a few years ago will carry that aspect forward. CO's 2 flights a day to TLV have a big emotional impact on Israelis..

And, again, if you're living in IAH/EWR/CLE you're pretty much stuck with CO. But other airlines are in that predicament too. DL has the biggest superhub and they offer PMUs.

CO is wholly uncompetitive when it comes to benefits. UA is making money hand over fist with their transcon PS service (so they say), and its hardly impossible to upgrade on them.

As for myself, I'm choosing to fly UA over CO because they offer SWUs and E+. SWUs that are subject to capacity controls, but nevertheless, usable. If you're not upgraded, you get E+, which makes UA a better choice over foreign carriers in Y. CO offers no such benefits. Are E500s/CR1s a pain to deal with? perhaps. BUT, they are much easier to deal with than having to guess and check whether or not EUA is working, or where your position is on the upgrade standby list. Plats are sweating out way too many upgrades for comfort.