I haven't pressed my binding in half for years. I know a lot of people insist on doing it because it's how they were "taught", but honestly I wonder how many people question why when they're taught this. It's like that old story about why you cut the end of the roast off before cooking it. The child asked why do you cut it? Mom said, well that's how my mom taught me so that's how I've always done it. So then Mom goes and asks the grandma, and she said "Because it's the only way the roast would fit in my pan."
I find that by NOT pressing the binding in half, it rolls around the raw edge of the quilt a lot easier, sits nicer on the quilt, feels fuller, plus I get to skip a step.