One of the fundamental notions out there I think is that somehow government is a business, it isn't, for a lot of reasons. Businesses operate to make money for their investors and as such, are very parochial, their orbit is basically "what is good for my business ie the owners and the investors". Yeah, I studied management too, and they loftily talked about "stakeholder management", but especially these days, that is as dead as the quill pen. The government by its very nature is supposed to do things that benefit the country, state, locality, they basically are an entity with many, many stakeholders. The government example funded a lot of basic research, one that didn't have ROI built into it, something the private sector is quite loathe to do. The government can and does provide services where the private sector won't (and often attempts to privatize what had been a government service fail because of the gulf between the 2). Government wired rural areas for electricity because no utility would do it, the same way today they are paying to lay in fiber to rural areas, because the private companies would never get back the cost of wiring a farm 10 miles out of town. Sometimes the private sector works with the government to provide an essential service, the bus I rode every day is a private company but they are paid by the state to operate it, along with what I pay in fares.
Sometimes the private sector benefits from government activity. Think of Conrail, they took over bankrupt, failed railroads (and not without a lot of squawking and complaining that freight railroads in those areas weren't needed, trucks were the answer, etc). The government from what i know ultimately lost money on conrail if you factor what they sunk into it in infrastructure repairs, modernizing freight operations, dropping routes that simply made no sense, yet they ended up selling a railroad to private companies that thanks to all that spending, is profitable for them. If private companies do things better, how come they didn't buy any of the bankrupt railroads? Even assuming still going railroads had a crack in their belly and couldn't, how come businesses that were doing well couldn't do what the government did, buy the lines, invest money, and turn it into an efficient,money making operation? The answer is simple, a private company would look at the cost and say "no way I can get ROI on it". The government looked and said "trains in that region are critical infrastructure, there are people who depend on those trains to ship stuff or the people who work for the ralroad for a living", said they couldn't let it fail, and ended up leaving a working business that the private sector would buy.
So okay, what about Amtrak and passenger rail in general? It comes down to the same thing, who are the stakeholders and what is the value of keeping it versus dropping it, but more importantly, rather than look at it as it is today (kind of like Conrail c1975), looking and saying "what could it be?". The current Amtrak model in many ways is lacking, because no one as far as I know has come up with any plans for it that to me tell me they ask that question. Among politicians, some could care less, others are of the mindset that 'trains are the past, the car is freedom, airlines are the best thing since sliced bread', others quite honestly are kind of rail fans who see Amtrak as a kind of giant layout (I appreciate that thought, of course). On the one hand you do kind of have to be a dreamer to ask "what can trains do?", you have to be pragmatic and say "there are places they make no sense", and put it together, something no one has done. Envisioning a nationwide high speed rail system that can compete with airlines is pie in the sky, envisioning a rail system that fits into current and future needs , HST where practical, regular in other places, that meets needs makes sense. Eisenhower sold the interstate highway system to skeptics as a civil defense need,which shut up the crowd who said "let the states or private industry do it, it is a boondoggle", knowing full well that as a civil defense system it was bupkus, his administration knew the economic benefits of it (I am sure Charley Wilson, ex head of GM, was dreaming of scores of GM buses, cars and trucks using those roads).