Why Broadcast search space required 4 or 8 CCE aggregation ?

Question

Why can t we use 1 or 2 in-case of broadcast transmission .

Answer 1

I think common (broadcast) search space use 4 or 8 aggregation level because it is used for sending the control information which is common for all the UE's & to detected and decoded by all users including cell edge users or users having bad channel conditions.
Scheduler use higher aggregation level to successfully decode the DCI .