I noticed this too but the competitor was similarly re-sized as well. I bought the competitor anyway.
I was talking with someone today who just saw a "Spartan Store Brand" (bargain brand) six pack of raisins with the old, larger size boxes, but the person wasn't sure if that was just some old packages on the shelf still, or if "Spartan" still makes that size box.
(I believe that Spartan brand is only available in a handful of states.)