To collect the potential ridership of a dispersed area on the border of an urban space without running bus routes to each persons house. Then they leave their cars in a big parking garage and get off the road, reducing congestion in the urban space.
I guess that it works in very low-density places that are close to the city or something like that. But the problem is that the parking takes up space, so, instead of having some kind of transport hub, where economic activity happens (as is usual next to train stations or bus terminals), you end up with a bus terminal/train station in the middle of nowhere, where the only thing you can do is take your car back to suburbia, and furthering its car dependency. And I'm not sure the regular driver is as city-minded as people here to think of the congestion and all that stuff when they decide between taking the car to the city or to the parking lot and then having to deal with the bus and its schedules.
Also, we're talking about buses, not trains. Unlike a train, you can take a (small) bus into a lower-density area, as it is the case in some cities.
