And how many of the writers you mentioned were able to juggle more than one novel in their head, with a full-time job in an unrelated field, and a family? And of the very few that did just that, how many of them succeeded quickly? One? Two?
Me? I'm a big F. Scott Fitzgerald fan. His outlines were sometimes larger than the books he was writing. Gore Vidal's pre-writing is where he rules the world of American Historical Fiction: research, note-taking, outlining, and etc.
My outlines are in the 5000-10000 word range, and my research notes fill multiple notebooks. I don't use all of it, but it's all in the air of the book I'm writing.
Not every outline is the same, nor every writer.
Think about it this way. Drive from Dallas to Denver.
I live in D/FW. There are two main ways to get to Denver. One is going west to the Rat Tong pass in New Mexico (slightly longer, but gorgeous desert scenery), and the other is hopping 287 through Amarillo, Oklahoma, and wiggling around highways to get to Colorado (shorter but it's like driving over one, endles field of rough grass).
When I start to drive to Denver, I have a map of the way I want to go. As I'm driving, I may encounter all kinds of weird detours, and weird sights and sounds that merit viewing. The weather may change, the roads may suck too much to continue this way,etc. The map isn't perfect. It's just the general guide in the best of circumstances.
If a writer just gets in his car with a piece of paper that says "Denver", he'd better already know the way. Stephen King, Bradbury, etc. have driven to Denver enough to know the way without being told. My Dad -- in real life -- used to live in Denver, and used to drive me up there once a month to do Drum Corps (thanks, Dad!), and he doesn't need a map to get there and to wiggle around on the way, because he's already been there so many times.
Stephen King, Bradbury, etc. are capable of doing exactly that. They know the way because they've driven it already. The very few writers that are capable of the metaphoric drive to Denver while juggling multiple books, another job or two, and a family, are the exception that prove the rule. It's so hard, only the most gifted can pull it off.
I know most of the way Denver. There are sections of the drive that I know very well, and places I don't know at all. I don't use the map all the time. I use it to get over the places that I don't know. When I'm stuck, I have somewhere to look. And, if, as I'm driving, I discover something about the road I'm on, or the tiny little town I've hit, then the map also helps me scoot over a few blocks, and still remain on the larger trail.
Outlines aren't about mechanical plot-writing. They're about efficiently pushing yourself through situations that may lead to writer's block. They're about keeping your eyes on the larger destinations.
If you don't use one, that's your concern, and obviously I can't stop you.
If you do not currently attempt taking detailed notes, I encourage you to try. You'll never really realize how much you forget until you start writing everything down.