DC's streetcar and subway systems aren't supposed to address the same need. The metro system, in terms of station placement/spacing, schedules, line routes, etc

DC's streetcar and subway systems aren't supposed to address the same need. The metro system, in terms of station placement/spacing, schedules, line routes, etc., is designed to efficiently move people from the suburbs to the core and back again. It's poorly laid out for moving people within the city; the hub and spoke layout means almost everyone needs to transfer and trips are often circuitous. For my commute to my last job, for example, getting to work via metro required walking five blocks, going into downtown, changing lines, coming back out from downtown, and walking an additional four blocks. It took 45 minutes, vs a half hour just to walk to work or ten minutes to bike, and this is typical of getting from place to place within the city by metro. Most people don't bother. The envisioned broader streetcar network would have been explicitly designed to address intra-urban trips, and would have had a very different layout from metro, with stations spaced more closely together, and fewer lines passing through downtown. Lots of cities have different systems to address these needs, since it's difficult or impossible to design a system that does both well.