Wow Cataclysm Patcher

Just why do we have to run a huge installer (5.29 GB) [which does *not* tell you first that you need more than 15GB free space where WoW is installed as temporary space btw .. I think it was about 16 or 17GB .. - problem is it just aborts and it does run for like 2 hours or sth like that ] but just after the installer we get the new launcher:

WoW 4.0.1 patcher

which tells you it wants another 1.6GB .. but you can start playing after about 600MB or sth ..