Because the attack perks are much stronger, take Battle Fury or Retribution, for example, and the first one can be taken already at level 1 of the attack skill.
Personally, I don't like this setup very much; I would prefer to see 10/20/30% attack instead of the symbolic 5/10/15, Battle Fury as a level 3 perk, and not level 1, and Retribution in leadership altogether.
I even have an idea to give Retribution to humans as a super ability instead of Unrelenting Force; this would at least allow it to compete with True Luck or, for example, Absolute Defense (it would still be weaker, of course, but Unrelenting Force is too weak an ability to be a super ability).
And about making Battle Fury a level 3 perk instead of level 1 – I completely agree, but maybe then we should also move Resilience (+2 HP) in defense?
Блистает там воздушностью прогалин.
Но между кедров, полных тишиной,
Расщелина по склону ниспадала.
О, никогда под бледною луной
Так пышен не был тот уют лесной...