Specific to Maine, I would say declining opportunity is the main (get it?) reason. My buddy in the military is from Maine and has gone back to do a week hunt with family for the past 8-10 years. Getting tired of not seeing any bucks, he is not going back this season. As someone noted, particularly in the past 3 years, Maine has had some tough seasons and its big buck reputation has taken a hit.
For myself, if I was going to pay for a trip out of my state (Va) to get a really big buck, I would consider Ontario, Canada way before Maine.