Originally Posted by
Mirek
Because for the manufacturers it's much more expensive, time consuming and complicated to work with the road car bodyshell than with the space frame. Imagine that whatever change happens in the road car may affect the rally car and if you need to modify the bodyshell for the rally car you have to go trough super expensive and super time consuming process of changing the stock production.
For the manufacturers the optimal way is to keep the motorsport department completely separated from the production. With that you can do the same change with handful of people and only within the motorsport department budget. In the other case you may need hundreds of people, months of meetings and plannings and a lot of money from outside of the motorsport department budget for the very same change (in the end you probably end with not executing it and stay with sub-optimal solution).
Moreover the stock cars are less and less suitable for being converted into rally cars. By requiring a stock bodyshell you close the door for large part of the pool of potential competitors. That itself is a stupid thing to do.
