That would be an argument for slashing service two or three months back when many people couldn't travel, or even possibly now when travel demand is still very low (IIRC, much of California is still under strict shelter-at-home orders) but IMHO not in October when, knock on wood, travel demand will have started recovering.
Some of the most severe (and IMHO reasonable) slashing of Amtrak corridor service during the strictest stay-at-home orders -- no Acelas, no Hiawathas, no Downeasters, no Keystones or Pennsylvanian -- have been and are being walked back with partial restoration of service. Running daily long-distance trains during that period but then slashing LD service in October becomes even more bizarre in comparison.
As to running mostly empty trains, transit providers keep lightly-used bus and train runs as a cost of maintaining a scheduled headway (e.g. 15 minute buses, or hourly trains) that the riding public expects. They run a half-empty 10am train so that people who usually take the full 8am train can rely that there'll be a train every hour. So potential riders don't have to choose between memorizing gaps in the schedule and conforming their lives to them, or saying f'it it's easier to just drive.
Same with Amtrak corridor service. I doubt every Acela or Keystone or Hiawatha has the ridership of the busy rush-hour runs, but cutting one lightly-traveled run in hopes of driving passengers to fill the preceding or following run would create a schedule gap that would discourage some passengers from choosing the train altogether.
Daily LD service is also the same. Nobody planning their travel has to think if today is a train day in their town, or they'll have to wait a day (or two!) to travel, if every day is a train day. Because if they do have to fit their lives to a 3-times-weekly Amtrak schedule, many will say f'it, it's easier to just drive.
