Approximately nobody is going to live close enough to the workplace of everyone in the household who works.
Then who is going to be left to support the walkable economy? You need approximately every working person who lives within that community to be active in the walkable economy, else you will quickly find that services are no longer within walking distance.
Are you imagining that you'll hop on the train to go work on the other side of town, while someone living on that side of town hops on the train to work in your neighbourhood? That is not a good reason for transit at all. That's just silly.