The weight sure doesn't help you if you have to climb 5000+ vertical feet in a day, but weight isn't the only variable. The reason pros ride heavy bikes is that they aren't willing to make the tradeoff for lighter-weight tires, suspension, brakes, wheels, tire inserts, and handlebars. Sure, pedaling an extra 5-6 pounds takes its toll, but how much does not having traction slow you down? What about worrying all the time about pinch flats? What about not being able to slow down? Everything is a tradeoff.