There's something that rubs me the wrong way about the term "commuter rail." It's as though the only reason anyone had to go anywhere was to get to work. The commuter-rail mindset is what gives us branch lines with peak-direction only service and nothing on weekends. It implies that people who want to go shopping, visit friends, see a show or even go to the doctor are going to do that by car. Even people whose work takes them to more than one place during the day aren't really commuters once they get to their base. Railfans, teenagers, families, lovebirds, the elderly - they're not commuters, so they're interlopers on the commuter rail line.
This is the kind of mentality that results in the disembowelment of formerly walkable, mixed-use streetcar suburbs to make room for acres of park-and-rides, or turns moderate-sized regional centers like Stamford into mazes of parking pedestals and ramps to underground garages. Because if you're driving everywhere, why walk or take a bus to the train? You'll be driving to the supermarket on your way home. And if everyone's driving to the supermarket, why put the supermarket where people can walk to it instead of cheaper land out by the highway? Easier for the delivery trucks.
In other words, commuter rail means sprawl. Park-and-rides mean sprawl. Maybe they've both got their uses as transitional stages; get people driving to the station, and then eventually you can build condos and a shopping center there, and eventually walkable infill, like they're trying to do in Virginia. Commuter rail has probably prevented the New York suburbs from becoming complete sprawly wastelands, preserving some walkable infrastructure until the time comes for everyone to start walking to the train again. Sort of a "suburb-banking." But it's a lousy way to think of trains, as just conduits to squeeze workers into and out of the job centers when cars fail. It's one we should try to get away from as soon as possible.
Of course, in practice there are hardly any few true "commuter" lines in the New York area today, those ones that only run on peak commuting hours. Ten years ago, the Boonton, Main, Bergen and Pascack Valley lines in New Jersey, the Danbury, Waterbury and Harlem lines of Metro-North, and the diesel ends of the Raritan Valley, Greenport and Port Jefferson lines all had practically no service outside of peak times. But now, thanks to heroic efforts on the part of New Jersey Transit, all those lines in NJ have at least some midday and reverse-peak service, and the Main/Bergen lines have impressive levels of service morning through night. Apart from the Main/Bergen lines service is still sketchy, but it's a lot better than it was.
Travel on those lines and you'll see that it's not just commuters and reverse commuters. It's people going from the suburbs to Manhattan for shopping and social activities, but also local college kids going to the various schools, college students from all over going home to visit family, nature lovers heading to the trails and parks. And even more so for the electrified lines where you get people shopping, dining and socializing in regional centers like Stamford, White Plains or New Brunswick.
If you plan train service for commuters, you tend to get people who only use the train to get to work. Plan train service for everyone, and you get people who walk for their daily errands and take the train for major shopping and socializing. And that's a sustainable lifestyle.