Tell that to the folks who ride the train between, say, Toledo and Chicago, or Trinidad and Albuquerque, or Minot and Havre, etc.
Look at the RPA data tables on LD train ridership. Most trips are a few to a couple of hundred miles or less. The percentage of Amtrak passengers actually traveling all the way across the country and spending 3 nights on the train is minuscule relative to total ridership. The only reason for a taxpayer-funded transportation company to provide premium service is that it boosts revenue, but the cost of providing the premium service shouldn't be so high that the
net revenue boost disappears. We really don't know how much it costs to provide traditional sleeping car and dining car service, and its possible that it's not as ruinously expensive as the anti-LD people say it is. However, if Amtrak can cut the cost of providing the premium service and not lose that many riders, they'll rake in even more net revenue, thus possibly reducing the need for a taxpayer subsidy for the coach service, which is where most of the ridership is.
I suspect that most overnight passengers would be perfectly satisfied with a flex-dining-like product if the meals were better quality and the menu had a some more variety. (And it was also available to coach passengers) Yeah, it would still suck (well, not be the finest dining experience) for three nights and 4 days on the rails, but why should the company cater to a small, demanding subset of its total customer base? Anyway, much as I enjoy the dining car experience, I don't ride the train primarily to eat, I save that for when I arrive at my destination.