Why must we sit through almost 1/2 an hour of Calculating Differences?

I've been sitting at my computer waiting for the game to update, and for well over 1/2 an hour it has been sitting on 33% and Calculating Differences. This happens every patch, taking huge amounts of time for something that seems to have no purpose. It used to not do this to my Knowledge, and if the game is just checking to see what files you have installed, why not just put a single file in that is updated each patch to tell what files you have? I don't feel like having to sit through 10000+ Files being scanned a patch, with it happening again on every patch update.

Sorry if i messed up in places, just got home from the Gym and i'm tired.