These lines last for a long, long time. Inevitably, they will provide transit for rich and poor areas alike at various times in their lifespans. Not to mention

These lines last for a long, long time. Inevitably, they will provide transit for rich and poor areas alike at various times in their lifespans. Not to mention that the people who work in a neighborhood don't always live there, and that includes people in low wage jobs who are especially dependent on public transit. Also, this particular line will relieve traffic on other lines that go through the heart of some rougher neighborhoods.