It's possible with carbon, but currently proving tricky to find something suitable (e.g Diverge with stupid hubs/axle standards). Just throwing stuff into the mix that ticks boxes and isn't huge ££££...
Carbon has nothing to do with it, discs are making things complicated as the whole experience is not refined and in early stages. But Hippy needs discs.
Why just ultra cycling races?
Lemond TDF steel bike etc.
Its 2016, there is no need to use steel/ti for racing unless its a preference.
^ also possible with carbon