Yes they are required. Over torqueing is just as dangerous as under torqueing. The studs will stretch to a certain point and then go back to their original shape which creates the holding power to keep the wheel in place. When you over torque, you go beyond the yield point and will not spring back.
This link is to an article that does a good job of explaining this.
http://www.crashforensics.com/wheelandhubfailures.cfm