> when 1 or 2 train tracks could meet the same demand and function

They can't.

You are treating cars as a way to get from point A to point B. Trains and buses are ways to do that. If cars were just a way to go from your home to downtown, you can in fact replace them with a train.

Yet if you build even very nice, very expensive trains that run frequently.. a bunch of people will still use cars. The train does not replace the car.

A car is both a set of abstract things (freedom, status, privacy) and practical things (storage, functional space, a moddable thing).

Build all the trains you want. Have high quality protected cyclist lanes. Have functional bus programs.

None of those things will replace personal vehicles.