You need to know where you're starting, and where you're going to end up, and what points you need to hit along the way. You can take some detours and circuitous routes in between, and some will be more interesting than others.
But while getting in the car and just driving can be fun, you might get really, really lost and end up nowhere interesting. Then you've just wasted time. If you're writing body copy, map it out. It will look like a bad, bulleted PowerPoint presentation, but it will help you stay on course.
(Speaking of copy and road trips, here's a link to an old Mark Fenske post I think is brilliant.)