Besides, costing three instead of two might actually make things awkward for people some of the time
Purple manipulates DON!!, allowing you to get more energy faster than the rules normally allow, letting you play huge Boss Monsters early (e.g., Leader Luffy )
Proxy cards can't be played in DCI-sanctioned events
In standard it was the core to the aptly named Puresteel Paladin deck, using its main ability to draw into more action and later on the metalcraft ability to cheat out on some equip costs, but it has also seen play in Cheerios, a deck based around 0 mana artifacts and Paradoxical Outcome to eventually cast Grapeshot, and most recently in Hammer Time, which focuses on Colossus Hammer, where Puresteel Paladin once again comes in to both help circumvent equip costs
Regardless of the effect, this mechanic does encourage aggression - or perhaps an alternate way of forcing your opponent to lose life - so keep that in mind if you decide to pick up these cards
It being an easy turn one play that will draw cards over the course of the game is amazing value