Tallulah Bankhead said, "Good girls write diaries; bad girls don't have time." To some extent, this applies to authors, as well. Writers are, by nature, the spectators in life. As children, while the rest of the kids were out playing ball, we were the ones in the corner, reading. At high school parties, if we were invited at all, we spent most of our time sitting alone and just watching everyone else have a good time. We studied the written word, body language, and characterizations. Thus, we're not generally social butterflies.
But in this day and age, promotion of our books falls mainly on the shoulders of the writers. You know all those glamorous book tours Hollywood presents as routine for authors? Fuhgeddaboudit. These days, unless you have a reality television show behind you, or an unlimited amount of funds, your "book tour" is wherever you can travel in a fifty mile radius. This means that writers can't afford to hide behind their laptops if they want to be successful. You have to get your face out there. Get your name out there.
So put away the shy routine. If people don't know who you are, how will they know you've got a book they might want to read? Authors can't afford to be another faceless, nameless part of the crowd. Be prepared to speak in public. The best time to start speaking is before you're published to help you get over your fears. You think no one's interested? Think again. A lot of people are fascinated by writers: where we get our ideas, where we find the time, what made us finally decide to try, and what's entailed in going from "idea" to "book."
Or you can continue to sit in the back of the room and be a spectator. But only if you want your book to go nowhere.