It's the difference between planners and not planners.
I have always gotten alot of flack for planning our trips/events, etc out so well. Now mind you, I don't mean planning every minute of every day, I mean simply doing research before I do something and having a game plan in mind...ducks in a row. Some people just don't get the difference.
There are people who think planning or researching for something takes the fun out of it, or they don't want to do the work. I totally disagree. For instance, my friends and family teased me alot about planning my wedding out so well, but the day of, I and the wedding party didn't have to do a thing but get fancied up and enjoy the day

. It was important to me so that everyone just had to, pretty much, show up dressed, ready to have fun and eat ALOT

. Everything went smoothly as clockwork, and no one had to run around panicking or figure out what was going on/how to get someplace/what to do next. I've been to weddings and in weddings where that wasn't done and *whew* it's a boiling pot.
It's the exact same way with a WDW vacation. People think "it's a vacation" and won't check anything out. Or the funny thing are the people who buy a guidebook, but don't crack it until they get there. They spend their whole time with their nose in a map trying to figure out what's going on (and how often have I seen these same people arguing?

)
They just don't get that one way or the other, you're going to have to do some coordinating. If you plan it in advance, that when you get there you don't have to cut into "fun time" standing around trying to figure out where to go, what's where, what to do next, where to eat AND, as mentioned, being in lines for most of the day. When something unexpected arises (rain, blisters, etc.), us DIS planners are prepared and the day continues on without much of a hitch.
Not to mention, all those people who don't research usually leave the park having missed out on a ton of things/sights because they simply didn't know they were there! (Those are the people who think they can see everything in one day

)
Planning ahead just diminishes stress and opens up time so you're not planning on the trip. On top of that, DH and I never felt like we were locked into anything b/c we knew what all our options were. It almost seems like planning ahead allows MORE flexibility in the long run.
But most people, they'll just never get it. They'll be eternal scramblers and havoc mongers (i.e. all my inlaws

)
P.S. You can always tell the planners: they're the ones who can afford to go take a nap at the resort in the afternoon without having missed one darn thing.