Sorry for all the reform questions, but why is it that the majority of the time the roman units get weaker with this reform?

I saw that the defensive stat went up for the hastati but it lost points on its missile attack and melee attack. Principes lose 4 points in attack and a point in missile but go up in defense and are expensive than their camilian counterparts, triarii go down in everything including price, and the skirmishers go down 1 in melee and up in defense.
Can you explain the overly drop in stats? I understand that the defense is going up as they learn how to combat the enemy better but why lose so much offensively?