North Philadelphia is a poor example of a place that doesn't warrant Amtrak service.
North Philadelphia is a secondary station in Philadelphia at which very few Amtrak trains stop, hence the low ridership numbers. (It was more important back in PRR days when the east-west trains did not stop at Thirtieth Street, the main Philadelphia Station, as they now do.) Any Amtrak train that stops at North Philadelphia also stops at Thirtieth Street which is Amtrak's third busiest station so it's not like Philadelphia doesn't warrant Amtrak service. But North Philadelphia today is also a station for two Septa lines (Chestnut Hill West and Trenton) as well as for the NJ Transit Atlantic City Line so there probably would not be any savings from not letting a few Amtrak trains stop there. They go through the station anyhow, whether or not they stop.
