Why are two of the AP items w/ CDR on hit?
Seriously

No wonder it's so hard to get 40% CDR on AP champions now.
And it's no wonder everyone is going
, because on top of the gold, it also gives you the option of building
.
If you don't you get caught in a trap where you either settle for 30% CDR or are forced to buy a terrible item...
These are the only items which have AP and 10% CDR. Even then the only AP items with 20% CDR are
... so unless you're going against a team which requires some MR, or if you're an attack heavy AP champion. Then chances are you're totally screwed when it comes to capping out your CDR...
As apposed to an AD champion who can just...
+ anything that builds from 
)