The most annoying thing (to me) on Amazon is the fact that some items can only be bought as PrimePantry shipments. I understand PrimePantry for heavy/bulky ite

The most annoying thing (to me) on Amazon is the fact that some items can only be bought as PrimePantry shipments. I understand PrimePantry for heavy/bulky items like laundry detergent. I don't get it for lightweight stuff like razor blades. I can't figure out why those items can't be bought as Add-On items to regular shipments.