The root of Tour de France was a celebration in human suffering and perseverance, with anything that undermines this frowned upon. In the original incarnations riders were self-supported including having to do all aspects of bike repair:
On the way down from the Tourmalet, Christophe was hit by a race vehicle, and his fork broke, rendering his bike unusable, and the rules said that he had to repair it himself. He walked more than 10 km down to the next village, and found a place where he could repair his bicycle. He worked on it for over three hours, being watched by race officials who made sure that he was not helped by anyone. When Christophe asked a small boy, of seven years old, to work the bellows, he was fined with ten minutes.
1913 Tour de France
The ability to persevere was what brought people to watch and follow the original Tour. Over time, the race evolved, and some rules relaxed, but perseverance of the human spirit still remains the top commodity of the race.
Arguably, anything that makes the race itself "easier" in terms of apparent suffering frowned upon by race promoters. This is likely why the race has had such a complicated history with doping. They can't be seen as directly supporting doping, as it could appear to diminish the perseverance component, but at the same time they realize the physiological demands are insane so they have at times turned a blind eye. As long as the race still appears "fair" and the riders are shown hurting, then everyone so to speak is happy.
These historical constraints and nods to tradition make it unlikely that the race will ever suddenly embrace bold new approaches. The interest has never been in "fairness" but in ensuring there is a good show of suffering and perseverance.