I think it's interesting that B6 never tried to rebuild an intra-New England network with the E-jets....opting to let CapeAir do.it with much smaller equipment. Anyone have a guess as to why the economics of New England/ upstate NY to BOS are so bad?
Most of the markets are relatively small and/or save little time over driving. Boston-Portland is a two-hour drive and a bit longer on the train. Boston-Burlington is three-and-a-half hours if you don't have a lead foot. Boston-Hartford is an hour-and-a-half. Throw in the relatively high fares needed to turn a profit and these markets aren't economically viable.
Keep in mind that the role of Boston as a regional air travel hub for New England partly stemmed from the fact that the small markets were often served with similarly small prop aircraft. Plus the carriers all interlined with each other so it didn't matter which commuter carrier was getting you to Boston. Speed limits are higher now and TSA makes flying a less attractive option compared to driving, so most folks will drive if the time needed to drive door-to-door is under four hours.
Obviously MVY/ACK are different because they're islands.