Following is from a 1920 public timetable for lines east. Plymouth could be reached by two different routes from Boston; one via Whitman (the present existing route) and the other via Greenbush. The two above lines joined at Kingston. The third line out of Plymouth ran to Middleboro and Taunton and in 1920 it had one round trip passenger train seven days a week. Looking at maps from this period it is clearly evident that the New Haven (and other railroads too) had more trackage than the traffic would support. A good number of these lines were cut back or fully abandoned not too many years after 1920, I have maps and employee timetables from this period and it was the same sad story everywhere, shrink, shrink and shrink some more. It was the same thing on lines west although probably not quite the problem that on lines east.
Sometimes a good customer (freight that is) would be located on one of these lines so the railroad would keep a portion of such line in operation in order to serve that good freight customer, some of them held on for quite a while for just this reason.