Both DirecTV and Dish Network use a Conditional Access System, Neither are compatible with each other.
All Dish Receivers have a Smart Card Slot, many of the newer Dish receivers have the current incarnation of their Conditional Access system encoded into the actual Circuit board inside the receiver. Once a Smart Card is inserted into the vacant Smart Card slot it disables the Conditional Access System on these receiver's internal circuit boards.
So even though the newer Dish receivers do not have an actual Smart card in their Card slots does NOT mean they are not using a "Smart Card", its just built into the receiver directly.