Because of the end purpose. If humans are accidents of nature, evolved from primordial soup, then we are not in need of redemption. God created man for His great purpose, man subsequently fell from grace and needed to be redeemed. We alone hold this unique position in all of the known universe.
You need to shut down your transmitter long enough for your receiver to function. The debate in this thread is not about whether man spontaneously arose from the primordial soup, it is about the validity of the catholic Churches endorsement of Theistic Evolution. The main point being that God using the laws of science that He created does not diminish the miraculous nature of His creations. If you are so hung up on the time the process took just remember that God created space and time and the relationships between them, but if you would prefer card tricks........