There's also a small matter of convenience. If I could walk to the corner, hop on a subway, ride to my stop, and then hop off and walk to my office/store/whatever I'd do it.

If I have to walk 20 minutes to a transit stop, make three transfers, and then walk another 20 minutes to the same... and that takes 3x longer that it did to do point to point in a vehicle.... then people are not going to do it.

Time is a precious resource as well.