Look the fact is Amtrak is looking to add "business class" seating to the Coast Starlight.
I'm not arguing that it would be hard to appeal to customers traveling on business between SF and LA... but I'm giving my opinion on how to structure a service to have a fighting chance to appeal to those customers.
The truth is that it is still a viable business model. Megabus just launched
Megabus Gold in England offering overnight sleeper bus between cities. I think there is an appeal to arriving in a city at the start of the business day, getting a good nights rest and avoiding the cost of a hotel in a city center.
As it stands the non-lie flat "business class" seating that Amtrak plans on installing on the Coast Starlight will only appeal to leisure travelers who are well heeled but don't have an overnight segment in their trip. There is an audience like that, but there is a wider audience that wants to be able to lie down and sleep, but doesn't want to pay for a roomette.
I'm also not arguing that an overnight train would survive after the introduction of CAHSR. But that's still more than a decade away. That shouldn't preclude Amtrak and Caltrans from trying something new in the meantime.