because all it is, is world building. the trick, I think, is to hold the world in your minds eye while writing. viewing it, seeing how it inner relates. If the world is there from the first word, perhaps you wont need to cut the first 3 chapters.
the first sentence...
the first sentence is as just as important as the last. with the first, we suck the reader in. We tell them by word choice what kind of book it is. We start with action, a kiss or a kick, but something that makes them ask a question ... 'what' or 'why' or 'who'? Some times the best first sentence is the question itself. 'Why would Ash kill Bobby?' .... Yes, why? asks your obedient reader.
I've been thinking of, and discarding first sentences all night. "She left with a wave and a bounce, the crumbling cement mortor crunching under her three year old trainers." but no... thats not the mood. And it doesn't make the reader ask any questions.
"Her parents were sorry to see her go, not because they loved her, but because it was less income, and they were afraid."... closer... but doesn't have the grittiness I want.
"Margarette stepped out of the refab apartment blocks and breathed the cold, dusty air deeply." No... no question
"Margarette clutched the payslip microchip so tightly, a sharp corner cut her palm. She didn't look back, she knew she would see her parents at the scared red door, watching her leave. It was her time, now! She was free of them, free of the labor, free of the company. There was the world before her, and she was going to seize it by the balls and wring it dry."