It can also be used to pay for additional costs that include generic mana
Mirrodin (20042005) Skullclamp was, quite simply, a mistake, and even with the best intentions and design practices, mistakes will happen (especially when dealing with new card types, like equipment in Mirrodin block and perhaps Vehicles in Kaladesh )
Though it generates card advantage, it is far less problematic than fetching new cards from your Deck, while also giving the opponent a chance to respond, as cards in the GY are far more vulnerable than cards in the Deck
Umbreon V 189/203 - Evolving Skies Holofoil Umbreon V 189/203 - Evolving Skies Holofoil The Pokmon Company During your opponent's next turn, the Defending Pokmon can't retreat
(2020-11-10) Although the ninjutsu ability has the creature enter the battlefield attacking, it was never declared as an attacking creature (for the purposes of abilities that trigger whenever a creature attacks, for example)