I don't see the reason for that, maybe it's to prevent serious accidents.. Well the speed will be less in the corners with restricted aero dynamics compared to last year, but still it will be fast.
If it were up to my I would have removed TC and automatic shifting from the cars, but else than that keep them to the shape rules as they had last year. I liked the way they looked
But again, if it's to make safer racing..sure why not.. but in the end, at least with the current development the last years they'll soon use drive with a keyboard with stabilizator in those cars lol..