the desire was to describe the internal aspect of the player classes that causes them to be what they are. When you roll a 3d6 you're actually setting your character up to be superior to the average human being. Simply rolling 3d6 results in ten or eleven on most rolls. This means that the average pc is "special" compared to the average of everyone else (which results in tens across the board).
The PCs are special in the way the great figures throughout history have been special. I wanted to encapsulate and help define what it was that made them so.
The Fighter example is among the ideal because it's so pointedly on. The Warrior, who effectively does EXACTLY what the Fighter does... can never surpass the fighter in terms of raw skill. The Fighter has more feats, as well as fighter only feats. A twentieth level warrior with the same stats and equipment as the fighter would get his ass handed to him on almost every day of the week.
Most guys on the basketball team could be equated with warriors... Michael Jordan would be equated with the Fighter.
This also is easily shown with the Barbarian. You can spend years and you'll still never be as good as Michael Phelps is at swimming, yet swimming takes relatively little talent. It's more raw "ability" than anything else. That's what makes the barbarian.
Seriously, take a good hard look at how the barbarian is designed and it's clear he's supposed to have good strength, dexterity, and constitution... and makes greater use of those ability scores than other classes, even other fighting classes.
Increased dexterity is more useful to the barbarian than the fighter because of his medium armor restriction and fast movement.
Increased constitution is more useful to the barbarian than the fighter because his constitution determines the length of his rage.
Increased strength is more useful to the barbarian than the fighter... and this is the thinnest of justifications... because the barbarian gains maximum effect of his special abilities from two handed weapons. Whereas the base fighter can go any direction, the barbarians special abilities benefit most when used in conjunction with two handed weapons.