Why won't states in the northeast raise their speed limits to 70 mph or higher?

There are plenty of roads in NJ, NY, PA and MA where the roads are as flat as can be, and people are averaging 75-80 mph on most of them. Here in NJ, people are going 80-85 in the left lane, and I have noticed this in states further north too. I understand that Maine is possibly raising their limit to 75. Maine is a state full of mountains and their raising their limit that high, where flat roads in the rest of New England and the North East are capped at 65.