I think it's going to depend on the amenity and situation. For airlines and such where there's relatively little competition, and leisure travel prioritized cost quite highly, I don't see that improving substantially - at best it'll go back to some sort sort of pre-pandemic lite service level.
For hotels I think it's a bit trickier. The biggest question is going to be whether certain amenities will get people to switch to their hotel over a different one. That would mean things like daily housekeeping may not come back or come back in a much reduced fashion, but things like breakfast may come back at leisure-oriented chains. Free breakfast is a selling point for a lot of leisure travelers, and I think some hotels will restore that and advertise it to win over travelers who value that.
As for the Amtrak lounge - pretty much depends on whether they think the lounge having food will win over business and sleeper passengers in a way that justifies the cost. It'll likely come back in some form (the fact that it's restored in many of the other lounges is promising) but hard to say what exactly that'll look like.
1) Business travelers (especially when paid for by the corporate bean-counters) also tends to prioritize cost very highly, except, I suspect they might be willing to pay for fully flexible tickets, so it's possible that an airline might find it useful to offer amenities in addition to full flexibility in order to stand out from the other airlines. Of course, because of hubs and such, many airports are near-monopolies, so maybe it doesn't matter. And with fully flexible tickets, you are paying through the nose (though maybe not in comparison with inflation adjusted fares from 50 years ago.)
2) I can't say much about hotels, as my usual criterion for picking one is location. The point about leisure travelers highly valuing a free breakfast is well take, however, many of the free breakfast offerings, even before Covid, were not really all that great. A known "bad" free breakfast won't cause me to avoid a property if it meets my needs in other ways. When I worked, it was not a factor at all, because if the hotel offered a free breakfast, and you ate it, then my employer would deduct the imputed value of the breakfast from my daily per-diem allowance, and their imputed value was highly inflated. Thus, I would prefer to buy a bagel next door and thus have a lot more of my per-diem allowance available for lunch and dinner.
3) The main value of having food at the Chicago Metropolitan club is that there are lots of passengers who are connecting trains and staying over lunch, and maybe they are reluctant to leave the station. On the other hand, if my experience in November 2019 is an indication, even in pre-covid times, the food offered wasn't really a substitute for the meals. On the other hand, most of the clientele of the east coast lounges are riding the Acela and Northeast Regional, and usually just show up maybe 20-30 minutes before departure. If they're traveling Acela First Class, they're going to be served food on the train, why do they need it in the station? If they're select Plus and traveling coach or business, I could see that offerings similar to those served at the Met Lounge in New York might be enough to bring on the train for lunch. Anyway, most of these travelers aren't riding for more than 3 hours, so the need to feed their faces isn't as great. Furthermore, they can always go into Pret, Au Bon Pain, or Starbucks at the station and get a sandwich, if the cafe car fare doesn't tickle their fancy. In any event, the food in the lounge, or lack thereof, isn't the deciding factor to these people (who are only a small fraction of the total passenger load anyway) on whether to take the train or go to New York by some other means.
(There is one exception in that the Washington Club Acela hosts sleeper passengers transferring between the Capitol and the Silver Meteor who are staying there over lunch. But they have never served real food in that lounge, only chips and snacks and basic drinks.)
While, of course, I appreciate it anytime someone offers me free food, I'm not sure that the food is the main amenity offered by these lounges. I think their real benefit is that they're a quiet place to wait that has more comfortable chairs than the main waiting room used by the hoi-polloi. Plus, if the lounge attendants are doing their jobs, you can also get extra services like getting reservations modified, ordering redcaps, or maybe even get a private escort to trainside. I've had pretty god experiences with the Washington attendants, but I've never needed any help when I've been in the Chicago lounge, so I can't speak about them.