A railroad is a business, and the first priority of any business is to make a profit. While preservation is great and all, that should be so far down on a company's priority list that it shouldn't even be a blip on their business radar. If a piece of equipment has aged and degraded to the point where it is costing more in repairs than it is making a return on investment then it is the railroad's prerogative to scrap it for the recycling value and to free up yard space and mechanical forces (both of which come at a premium). If a museum approaches them (or they approach a museum) to purchase the equipment or to have it donated then it is just icing on the cake at the point, even though the railroad has no obligation to do so. This doesn't even cover the costs of taxes, and insurance, and tariffs, etc.
Most people riding these trains daily don't know a Silverliner from an ACS, they just know they paid money for the right to travel on it, safely and efficiently. It is the railroad's obligation to provide that as part of their end of that business transaction. At the end of the day any retired equipment donation is simply a tax write off to them, that may or may not be more financially beneficial than simply sending the equipment in for a scrap paycheck.
Would it be great to see more equipment preserved? Yes. Does everything need preserving? No.
If you really want to make a difference in railroad history and preservation then consider joining a museum or railroad historical society. Hell, even just visiting and riding at railroad museums make a big difference in various preservation efforts. Repeatedly criticizing a public transit agency on a fan forum (where they are 200% not likely to read it) for not doing something most, if not all, public transit agencies do not do is not worth nearly as much as going out and volunteering (for example, at the RR Museum of PA where they have a saved AEM-7, or joining the Electric Railroaders Association, a group that organize shop tours and regional trips).
"That sapling that once grew just south of Wassaic may be long gone, and the Harlem Line’s appearance may have changed over the years, but for decades to come, I can count on it continuing to provide me with funny recollections"