Attributes are required to equip gear and skills. The three attributes also grant some passive bonuses: Strength grants +0.5 life and +0.2% melee physical damage per point Dexterity grants +2 accuracy and +0.2% evasion per point Intelligence grants +0.5 mana and +0.2% energy shield per point
Therefore the +10 attribute passive skills effectively grant: +10 Strength: +5 life, +2% melee physical damage +10 Dexterity: +20 accuracy, +2% evasion per point +10 Intelligence: +5 mana, +2% energy shield