My daughter and I actually had this argument this weekend when I was once AGAIN crying while watching Avatar for the twentieth time. The blue-alien one, not the little elemental-wizard-kid one. (Hey, I also cry at the end of Cool Runnings) Tami's a very literal, in-this-world twelve-year-old. She likes to read, but she doesn't understand how a writer--and hopefully through the writer, a reader--can become so emotionally invested in a world that is, in her opinion, FAKE.
I care about my characters. I craft every word, emotion and reaction with excruciating exacting detail. I second-guess myself countless times. I HATE throwing my folks in harm's way, even when I know it's necessary for both growth and drama. I know someone's going to curse me for killing off so-and-so, no matter how noble the loss. In order for a character to be more than black-on-white on a page, they have to laugh, weep, lose, win--and love. If they don't quake with fear, if their hearts don't stutter and shatter--neither will the readers.
Writers were readers first. We've worked hard to emulate the masters we admire, and we know what is is to set a book aside that's been "meh." We shudder to think of someone doing that to our baby. And our characters ARE our babies, our creations, from nothing but dreams and hopes and imagination. We breathe life into them, we cheer them on and comfort them when everything's going wrong... "Trust me," we tell them. "I've got this handled. You WILL see each other again..."
Characters ARE real. They have lives and back stories, hopes and fears and dreams. They worry, they cry, they get sick and injured. They can die. But they also personify all that is best and pure in ourselves. They do the things we can only dream of. They win the battles we can't. They're bigger than us, greater than us. And we love them for it.