They are not aftermarket in a LOT of engines. The Chrysler big block, Ford Cleveland series and Early Chrysler Hemis are but three examples where they were used stock. Although no small block Chrysler came with one, they are a good addition.
Thanks for the clarification. Like in the BB Mopar, an OEM valley tray is needed to keep the oil "IN" in the engine as a matter of design. Keeping oil off of the bottom of those intakes is an OEM design benefit.
