One difference between southeast Colorado and Kansas is that the line has a number of small towns along it, Trinidad, La Junta, Garden City, Dodge City, Hutchinson, etc. There are no towns and no stops west of Phoenix metro to support the service, heck, there isn't even a paved road.
What is it about those towns, really? Isn't it just that they were vocal and outspoken? My suspicion is that too many people and businesses in the Salt River Valley are indifferent to bringing the Sunset Limited back to Phoenix. The similarities between the Southwest Chief route and the Phoenix line are that they are both former premier passenger lines that the parent freight railroad lost interest in. I suspect that if the states and the feds would invest in the SW Chief line with good track, PTC and CTC then, voila ! The BNSF will suddenly and miraculously become interested in keeping the line. (That's kinda sorta happened with the Devils Lake line in North Dakota).
My prayer and wish is that if the Sunset ever returns to Phoenix, they could offer stops at Gilbert, Mesa, Tempe and Buckeye as well as downtown Phoenix. All those communities have witnessed explosive growth in recent years. And let's check baggage to Phoenix and at least one other stop for crying out loud! I mean, after all, "snowbirds" who head to Phoenix for an extended winter stay are gonna have some luggage with them!
What I have always lamented as a very, very sad development was that the community of Tempe labored long and hard and waged a valiant effort to establish an Amtrak stop in their community. After trying for years, and rehabbing the old SP depot using largely local funds, the day finally, finally, FINALLY came when they were met with success. Or, so they thought. Once Amtrak began calling at Tempe, they only stopped there for a couple of years before they vacated the Phoenix line altogether.
And so it has gone with intercity rail passenger advocacy since 1971. Just when you think you have made some progress, that progress is lost again or "vaporizes". There are so many, many examples of this. The Phoenix line is only the tip of the iceberg. I could cite many other examples but I strongly suspect that most of you on this list are already aware of them. Will America EVER have an adequate intercity rail passenger system that's an improvement over the third world? I hope so but it's sure easy to become discouraged.