Because to get the same amount of travel as with the long shocks you would have to mount them further inboard. This would work theoretically but you would have to majorly rethink springs and oil/piston combinations as the forces are completely different
(der Hebelarm is mit dem kürzeren Dämpfer ein ganz anderer)
I think they put the shocks out that far out of two reasons:
1. It's always been done like that
2. You get more consistent damping as the piston is "slower" when mounted further out on the wishbone.