I don't know of anyone who'd eat the skin of haddock. Unlike some cod fillets, haddock fillets are always sold skinned. When smoked, the skin is left on to prevent the fish falling apart.
You can eat haddock skin of course....if thick fish skin is one of your "likes". I always cook mine with the skin on but leave it on the edge of the plate....although haddock is rather like cod it has much smaller flakes and so i agree that the skin is there merely to keep it together and not really intended to be eaten!