Remember. The fist bikes were mtbs. There was NO pave'. Pavement, was invented for bikes . As was the pnumatic tire . That said, If YOU do not own and ride a road bike, you will never realize your true biking potential.
All pros', even downhillers ride road. Most serious Sport class, and all Expert class racers ride road. Don't kid yourself. Lance rules. leg power rules. Trees rule. Dirt is sex. Cars F***in' suck!