Greater Greater Washington goes into detail why buses are cheaper then Amtrak (they don’t have to pay for their "tracks" for one) and I will assert those reasons are the same as why Amtrak really will not allow bikes… "there is very little room on the existing railroad to add new trains." and most seats are sold.
This is why it makes sense to drop billions of dollars in subsidies for roads and next to nothing for everything else. ???
https://greatergreaterwashington.org/post.cgi?id=11732
Biking in Baltimore