You understand that powerful big-shots actually ride the train regularly between New York and Washington, enough so that they would qualify for lounge access on a routine basis. Some of these big shots actually have political power over Amtrak's appropriation, and if they don't have that, they might be media big-shots who can make a difference in Amtrak's presentation to the National media, or they're financial big shots who might have some influence on various financial aspects of Amtrak. If I were Amtrak, I would definitely want to make such customers happy, very happy. The only question I have is why they haven't upgraded the lounge in Washington.
On the other hand, the lounge in Chicago is mostly used by retirees and train buffs who are riding sleeper coast to coast, plus local folks riding business class, who while they may be accomplished professionals in their fields, they aren't the Masters of the Universe. There may be some west coast media moguls who ride Amtrak out of LA from time to time, but it's just not the same thing. The most practical way to get to DC from LA is by flying, so the west coast bigshots are more likely to be found at LAX, not LAUPT.
For this reason, Amtrak may have more of an interest in providing an exceptional lounge product at the New York hub as compared to their lounges in Chicago or LA.