The challenge is one approach only needs to modify the transit infrastructure. The other means having to tear down and build new commercial and residential properties and force people and businesses to relocate in order to have a vaguely sane transit system. My area desperately wanted to do transit but even with rather significant hypothetical funding, they could only service about 10-15% of typical trips. They’ve settled on a plan that is much less money, but only serves like 5% of trips. To go with that plan, they are making restrictions around zoning to force mid density mixed use construction only, favoring one of the two chosen transit corridors.

They are trying but just people are distributed very awkwardly for mass transit.