Obviously personal aesthetic preference plays a role, but this is one of the things I really despise about the current subway map. There was very little need to add in the geographical features with the harbor/river outlines, but doing so gives the impression of place to stations on the map, which is all well and good for the downtown core where it's not far off, but really problematic for the Green Line where it implies, completely erroneously, that there's an enormous distance between some stations (i.e. Chestnut Hill Ave, Cleveland Circle, and Reservoir) that are very close together, and vice-versa. It's a schematic map that holds itself out as a geographic map, but worse it's one that's partially accurate and partially not as a geographic map.
(The other map pet peeve is where it shows the Green Line crossing under the Orange Line at Haymarket. It might have technically been accurate for a brief period in the 1990s, but it's not accurate now. It doesn't harm wayfinding, but it is a glaring error to anyone who really knows the system.)