A part of this we can lay to a stressed equipment fleet.
Let's take the example of the Santa Fe, using the Chief and the Super Chief/El Capitan during their daily service.
To run an 1800 mile route, each of these trains ran with 5 sets of equipment ... Two sets leaving the Chicago and LA termini daily, two sets midway on the route (due into the termini the next day) and a fifth set at the coach yard cleaning and re-stocking ... and available for emergency protection at that termini.
Further, the SF had sufficient older (but suitable) equipment to make up an emergency consist. Quite often the public timetables carried a note that stated "equipment is not guaranteed."
It does not really matter the road. GN, CB&Q, NP, UP, SP, IC, and so on... many ordered a spare set of equipment to protect the service of their trains, and they also had adequate "hand-me-down" coaches and Pullmans in hand to take care of any emergency.
As we've seen in this thread, Amtrak has an emergency consist at LA: Horizon cars and their very last dome. Amtrak operations folks have used that to get folks into Arizona to meet up with the Sunset when they annul the WB Sunset in AZ.
I understand Mr Gunn's capital requirements for rolling stock and real property maintenance, as he's placed in his recent official reports. I trust and hope he will advocate continued capital procurement for his rolling stock. An adequate fleet helps improve system-wide service.
John