(IMHO) as this enables third party extensions and site managers to develop better login integrations (they currently tend to redo custom login forms (e.g. forums, ecommerces etc. that ask a login to continue to a page) that is bad in my opinion as they should leverage on the existing login page)
Also i'm not sure if the $this->form->getValue('return') can be removed (i think it's old legacy inheritance, but you should check)