"Near lockstep"....there are carrier's (although not always a choice), that do try to offer a better comfort and service experience in some markets. So some consumer's do have a choice, but most of them will still go for the cheapest fare available.
With so many mergers draining our domestic competition and so many major airports converted into nearly impenetrable fortress hubs very few consumers enjoy useful options for domestic trips. There is still some competition on the East Coast <-> West Coast routes but other than that it's slim pickings. Outside of the brief window when one airline says they're removing/monetizing something and the other airlines fall in line there are few if any meaningful choices for most of us.
If consumer's would reward those carrier's with more business, the "near lockstep" might go in the other direction.
Here are the airlines that serve my city.
AeroMexico, Air Canada, Alaska Airlines, Allegiant, Delta, Frontier, Interjet, American, Southwest, Volaris, and United.
I've tried seven of the eleven and so far as I can tell they're all using the same playbook. The only difference is how quickly they turn the page.
Personally, I would like to turn back to the regulated era, when the old CAB set the fares, and carrier's outdid each other with either faster planes, or better on board amenities and services to compete.
If that were the case today we'd probably be paying $5,000+ for a domestic trip. I don't have a problem with booking Main Cabin Extra or Comfort Plus or whatever but when a double cost upgrade only buys me 33" of pitch I start to wonder how long it will be before I'm stuck buying first class in an industry where coach class is quickly becoming child sized and premium cabins appear to be shrinking into oblivion.
Edited by Devil's Advocate, 22 June 2018 - 10:54 AM.