Even into the Mid 70's there were plenty of TDF stages which went over unpaved roads, sections. Mostly in the mountain stages.
If it's a road, its fair game for a stage. Riders, unfortunately will succumb to difficult conditions, often due to some other rider's error. So goes the war
And some times from their own mistakes - Kruijswijk and the Giro, Schleck and the TDF.
It's an equal playing field for all starters - what they make of it is the game.
All of this is way more 'equal' than the spectator scrum - don;t see any calls for stopping that...
Ride On thru
Yuri