more about the MBTA

Why isn't the commuter rail set up for commuting in both directions? There is *one* morning train from Boston to Newburyport. If a person were to miss it (which is something one has to plan for, if one is taking a bus and 2 subway rides to get to the Boston end of the train), there's not another train to Newburyport until lunchtime. There are lots of inbound trains in the morning. What do they *do* with all of them? Just park them downtown until it's time for the afternoon outbound trains?

ETA: The Providence line looks like the exception, because outbound from Boston is inbound to Providence. A hiring manager just asked me if I was intending to commute from Arlington to Stoughton, and I said yes without specifying that I meant to do it on the T. If it turned out to be too horrible, I could move.