This remains one of my favorite maps I've ever seen on twitter. To add some commentary to this map: The entirely in-city lines: Cynwyd, Fox Chase, and the Chestnut Hill lines are the four lowest ridership lines in the system. https://twitter.com/christofspieler/status/1201688524757577728

In addition they are among the worst lines for ridership per kilometer:

Elwyn 457
Main Line 370
Airport 367
Norristown 338
Warminster 292
Lansdale 289
Chestnut Hill East 284
Fox Chase 277
Chestnut Hill West 273
Trenton 213
West Trenton 207
Wilmington 160
Cynwyd 59

The Cynwyd line's service is a joke and so is the ridership, but beyond that the only lines that perform worse than the in-city lines are long distance regional lines that reach into other states.

So what exactly does SEPTA have to lose? The lines are low ridership with no long distance commuters to placate. Finish giving the lines high platforms, make sure you have track for 10 minute headways, and lower the fares to same level as the subway. After all what's to lose?

The Concrete is almost there, the electrification is there, all that's lacking is a basic attempt at decent operations.

Also @christofspieler has an intuition deep on the above thread that the old West Chester line would be a good place for rapid transit service, and the ridership per kilometer here seems to bear that out.

I'll leave this thread with two pictures: On the Left is Shibuya which basically has ten tracks. On the Right is North Philadelphia with twelve. Run good service, allow dense buildings, and ridership will come.