Why do we allocate common control resources of a cell = 24 RBs x 2 Symbols?

Dear all,

Why do we allocate ((common control resources of a cell = 24 RBs x 2 Symbols)) when ((Occupied Symbol Number = 1)) since CCEs will be wasted compared to ((common control resources of a cell = 48 RBs x 1 Symbol)) with ((Occupied Symbol Number = 1)), assuming rate matching is off?

Thank you.