This.
Roughly 20-25% of people in the West (depending on country) are smokers. They continue to do so despite knowing the health risks and looking at pictures of blackened lungs each time they get their cigarettes out. By the same token, I reckon calorie data on menus will not stop the obese (i.e. those most addicted to overeating) from choosing whatever high-calorie food they want in that moment. It's the sort of information that will be poured over by the already calorie-conscious members of society, who tend to be as skinny as Jennifer Aniston already.
Several friends that I go out to eat with are struggling with their weight, and pay attention to calorie information when it's present on the menu -- taking their best guess when it's not. It's often quite surprising what's really going into food and where high-calorie additions are hiding. And I know first-hand that a calorie listing has persuaded a friend more than once to change their menu selection.
There's a significant middle ground between the Jennifer Anistons and those who have completely given up caring. Most people I know are in that middle ground. These changes help us make better choices.