The first draft exists to find out what the book is about. That is its whole job, and it is not a small one. The second draft is where you accept the answer.
I cut roughly a fifth of every manuscript between the first pass and the second. Almost all of it is scaffolding: chapters where I was explaining the world to myself, scenes that arrive at a conclusion the reader reached two pages earlier, and the sort of careful throat-clearing that makes an opening chapter feel like an apology.
Before a chapter goes, it has to fail three questions. Does anything in it change? Would a reader notice its absence? And is the information in it available anywhere else? A chapter that survives all three stays, however long it took.