It's a lovely idea that - if you're talented enough - books simply flow from brain to page. I wish! Maybe there are some extraordinarily talented people around for whom that's true, but I simply don't believe it. Yes, it's tedious writing stuff out by hand and I can see how now we all use computers, it may appear incredible that anyone writes out a whole novel by hand, corrects it, and then writes it out again, but it's what people used to do.
Obviously you wouldn't want to do it too often, so pre-computer age writers were more careful about what they wrote, but I don't believe there were many single draft manuscripts about. Those who wrote serials - Dickens, for example - didn't have the opportunities to correct their stories once they'd gone to press, but I think all writers take the opportunity to revise if they can. And if that means handwriting several drafts, so be it.
And if anyone says otherwise, well, writers lie! We don't always want to expose our working practices, so smudge over the truth. Perhaps it sounds better to some if a writer is taking dictation, as it were, from their subconscious rather than doggedly writing and re-writing until you've got something worth publishing. Some writers may indeed wait for inspiration from their 'muse' before they put pen to paper, or finger to keyboard, but none that I know of.
Writing is creative, but it also involves hard work. I'm not a very disciplined writer personally, but at some point I do sit down and actually write enough consistently to make a novel. I don't wait for 'my muse' - if I did, I'd not be able to pay the bills.
Sorry this has come late - I'm still without internet access at home - and have been reduced to writing this in a beautiful hotel with WiFi, sipping a delicious cup of tea while I stare out at the lawns stretching towards a verdant valley...