I think you will find that adding Disc brakes to a Road bike makes it no heavier and quite blatently has significant advantages over caliper brakes.
Its rather silly to use traditionalism and conservatism as an argument against technological advantages.
I would suggest that sharper braking would lessen, not increase, the amount of crashes. It would certainly, in certain cases, limit the amount of people effected by a crash. The idea that people would suddenly start hitting their brakes and get hit from behind is a bit over the top really. They are easily adjusted to stop them being "that" sharp. Additionally, most road brakes would move immediately to Carbon or Ceramic compounds, which are going to be less abrasive then current mountain bike styles.
I would also suggest that in the wet - there would be massive advantages. As someone who rides with Swisstop pads on Carbon Clinchers, I am literally terrified by the prospect of riding long descents in the British rain. We have a rather large amount of 1/4 and steeper descents (ie, steeper descents that most places), with sharp and blind corners. Effecient braking from disc brakes would be exceptionally useful and far better than my current situation.
As for weight, give me a brake. This is simply not going to happen. If manufacturers were allowed by teh UCI to experiment and alter the way in which their bikes were made, they would be safer, stronger, more effecient and far lighter.
Now for the example! The Beru F1 systems Factor 001. Very impressive road bike. Strong, light (under 7kgs and around the UCI limit). This has disc brakes with a Carbon-Ceramic Composite - which is not super sharp, nor is it impacted by water or heat, in the same way caliper brakes are. For all those lost in the 19th Century, welcome to the 21st.