UCI has strict regulations on the geometry, weight and even ancillary equipment (think brakes, gear shifts) of bikes. I vaguely recall the minimum weight being

UCI has strict regulations on the geometry, weight and even ancillary equipment (think brakes, gear shifts) of bikes. I vaguely recall the minimum weight being something like 14.9 lbs, but this is likely incorrect. Point is, it's quite possible to make a bike that is lighter than this while still remaining safe for racing. I've heard of some using lead ballast to make weight. One advantage of this, though, is you can choose where to place the weight, such as in the bottom of the frame, near the crank, lowering center of gravity and helping stability a bit. The regs do make for some funny situations though. Take a look at a pro peloton and look for the shortest rider, preferably someone close to 5 feet tall. Their bike will be comically oversized for them. The UCI tends to be a fairly conservative organization that favors tradition over accepting the latest technology and design trends, especially with road racing. You're more likely to see new technology in non road disciplines such as cyclocross or mountain biking. Just see disc brakes only just getting into road racing in the past several years (I've not been following racing closely anymore, so not sure when).