Why does the Audi A7 have an optional sport differential?

I've noticed that the Audi A7 comes with the option to add a sport differential, but what exactly does it do and why is it considered an upgrade?

The sport differential is an electronically controlled torque vectoring system that allows for better handling and stability in corners, making your driving experience more precise and dynamic. It's considered an upgrade because it enhances the already impressive driving performance of the Audi A7.