Maritimes:

- New Brunswick is very economically depressed and only has a few things of interest to your average tourist (primarily along/near the Bay of Fundy). It's about a 8hr drive just to get to Moncton from Boston.

- Nova Scotia - Also struggling economically in many areas outside of Halifax. Halifax is 11hrs out of Boston and what's arguably the most interesting scenery in the province (up in Cape Breton) is more like 13hrs.

It's also cold much of the year so the optimal tourism season is short and even in the warm months it's often not that warm (and the ocean water certainly never is).

Quebec:

- Quebec City is decently known and about 7hrs. The rest of the province besides that and MTL I agree are basically a mystery to most.

- That Maine is basically a remote wilderness along the Quebec border and has almost no land connections (and no good ones) makes exploring up beyond Quebec City less common than it seems like it should be. (Also no bridges over the St. Lawrence beyond Quebec City).