Story is Character. That’s the famous quote from Robert McKee. Story is character. Character is story. Meaning, without character, you have no story. Your character drives the story, your character makes the reader invested in the story. Without a character the reader can relate to, at least on some level, or sympathize with, or care about, the reader will be dissatisfied. Yes, you can certainly write a fabulous bestseller without characters you care about (I can think of at least one thriller I read this year where I hated the characters and hated the ending, yet couldn’t put the book down), but it’s much, much better if the reader is rooting for your protagonist.
Character drives the story — as Toni McGee Causey has often said, “Story = Character + Conflict.”
My characters either walk up to me, fully formed, and I simply tell their story; or they are stubborn and I have to write and rewrite to coax out their essence. Even fully-formed characters need work during revisions, to layer in the depth that makes a good story rock. But the stubborn characters — they take time. And sometimes it takes a lot of fighting with them to finally understand what makes them tick.