On the first part they do here because of the cost and time factor. The cost being primarily parking rather than gas, even now. Traffic also sucks - even when a large majority of the over two million folks working in Manhattan use public transport, that still leaves quite a bit of road traffic trying to get onto an island with a limited number of tunnels and bridges. The MTA has been responding to increased commuter traffic by using longer and more frequent trains. On the suburban to suburban commutes, I agree there is no short term solution, but it would be nice if we got started on using zoning laws to shift employment to mass transit hubs.

One rather interesting very recent development has been companies offering shuttle services from suburban/satellite urban commuter rail stations. The primary reason has been the growth in reverse commuting by young professionals who absolutely hate the idea of living in the 'burbs.