Traditionally there were 3 saving throws (checks made in response to an action) that there tied to 3 stats (dexterity for reflex, fortitude for constitution, and will for wisdom) making those 3 stats more valuable. Additionally, there were skills tied to specific stats.
Strength got a skill or two, dexterity has several, constitution gets no skills, and then several skills spread across the mental stats. Making those stats more valuable. Then we have weapons. Melee used Strength, unless the weapon was light or finesse.
Then you could use Dexterity. Dexterity also counted towards your Armor Class (how hard you are to hurt). All of this resulted with Dexterity being far and away the most valuable ability score. Several different systems have gone to a 4 attribute set up.
Making each more valuable. We are going with 7 attributes; breaking the defensive aspect of Dexterity off into Agility and tying it to the Reflex Save. Adding a 4th Save tied to Strength, Might, gives us a more even distribution.
Strength for melee, Might Save, and carry. Dexterity for light and ranged weapons. Agility for defense and Reflex Save. Constitution for HP and Fortitude Save. Intelligence, Wisdom, or Charisma may be used for Will Save and Magic.