I don't use them either (except for baked goods, mostly) but I do use reference books on occasion and, sometimes, some cookbooks as references. They are good for ideas, techniques, familiarizing oneself with the unfamiliar, self-teaching, etc., and are indispensible for the professional cook--or for one who either aspires to cook professionally or for the serious cook looking to increase skills or repertoire.
In no particular order, a few of the many I like:
The Professional Chef Culinary Institute of America; A Produce Reference Guide to Fruits and Vegetables from Around the World: Nature's Harvest Donald Heaton; Vegetables from Amaranth to Zucchini: The Essential Reference Elizabeth Schneider; The Cooking of the Eastern Mediterranean, Couscous and Other Good Food from Morocco , and The Cooking of Southwest France all by Paula Wolfert; Sauces: Classical and Contemporary Sauce Making James Peterson; Charcuterie: The Craft of Salting, Smoking, and Curing Michael Ruhlman and Brian Polcyn; Great Sausage Recipes and Meat Curing Rytek Kutas; The Cake Bible Rose Levy Beranbaum; Maida Heatter'S Book Of Great Desserts Maida Heatter; Classic Indian Cooking Julie Sahni; The Silver Palate Good Times Cookbook Julee Rosso, Sheila Lukins, and Sarah Leah Chase; On Food and Cooking Harold McGee; Molecular Gastronomy: Exploring the Science of Flavor Hervé This and Malcolm DeBevoise