Could the actual reason be historic? That being, because Maine was technically part of Canada for a short time after the British "took it over" in the war of 1814 -(but gave it back later, because it was just too peaceful).

:)

""Nova Scotia Lieutenant-Governor Sir John SHERBROOKE led a force from Halifax into Maine, capturing Castine on 1 September. By mid-month British forces held much of the Maine coast, which was returned to the US only with the signing of the peace treaty"" Source, Canadian Encylopedia