Because in Offroad Simple is better! Look at all the other ideas that were floated around, and it seems the basic layout is always here to stay. Look at the Tenth Tech Predators, they were cooler than heck, but broke a lot too! Hot Shot comes to mind too, single shock front and rear.
It has to be easy to tune without a masters in engineering.
Here is a pic of a Truck someone tried to reinvent the front suspension on, Just to give an idea of complexity.