I literally say my reasoning in my comment. It's much harder to light up the outdoors for outdoor activities after work/school. I can't use sunlight in the morning for anything other than a wake-up aid.
But regardless, I still disagree. You seem to be assuming that early risers don't want to do outside activities, but that is not true. There are plenty of people that go for a run or jog, or morning hike, etc before work. At a previous company we had a rock climbing club called, "Get High in the Morning" :-D
One of the benefits of living in Utah, great rock climbing was only a 15 to 20 minute drive from the office.