In fact, I call my first drafts the "kitchen sink draft," because I throw in everything but the kitchen sink. I have a general plot in mind, but I toss in other characters and events if I think they're interesting. I don't do much revising; I just carry on to the end which, believe you me, is hard enough. With the first draft, there are so many decisions to make - if this happens, then this could result, or this, or possibly that. Which one works best? Whose point of view should I use for this scene? Is that idea going to work, or is the new one better? It's like I've got a really old map with lots of detours that I'm trying to read while in a very jittery car.
Then comes the second draft, aka The Winnowing. This is where I decide what's working and what's not. There's a whole lotta cuttin' going on - events and characters. Yes, I sometimes decide to get rid of a character completely, or combine two into one. This draft inevitably winds up being short. But I don't worry, because next comes the third draft.
I'm working on a third draft now, and it's occurred to me that this is where I start to enjoy the book as a whole. The most difficult decisions have been made in terms of story and character, so I can relax a bit. This is also where I start to put in a lot more of the "color" - descriptions of clothes, food, furnishings, etc. I ramp up the sexual tension whenever possible. Sometimes I discover I've made a major plot error in terms of timing, or I've made a character act out of character and that has to fixed, but overall, the process is a bit easier. Yet I'm still not done.
Hopefully, though, when I get to the fourth draft of a book, it's just a matter of smoothing out the prose, looking for repetitions and typos, adding a bit more color, or correcting the occasional continuity blip. Generally, this is the final draft before I send the book off to my agent. Not always, though. I've done up to seven complete drafts, and many more of individual scenes. I want to, as Ernest Hemingway put it, "get the words right" and I keep editing and revising until I think they are, no matter many drafts it takes.