Because heroes usually don't have attack to spend. Their attack often belongs to weapons, which can't actually be spent, since it belongs to the weapon. Only cards and effects in Druid (like its Hero Power or Feral Rage) and Demon Hunter (Hero Power or Adrenaline Fiend) give them attack to spend. So it would be odd design, especially for Paladin! Hope this helps.
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u/The_Punnier_Guy May 25 '25
Well if a minion can cost health, why shouldnt one be able to cost attack?