People run by and large because they like it.
Runner's high is no myth. Running by yourself for three or more hours can be extremely lonely, especially when blood sugar levels start to drop or weary hip flexors reduce your stride to a shuffle. Thanks to area running stores, those long runs don't have to be lonely at all. Here are some organized long-distance training runs, where if you're going to get fatigued, you might as well do it with plenty of company. Don't park in the nearby church parking lot.