Patryn of Elvenshae said:
Strength, in an "Average Gaming Session" - as in, one that involves a good mix of combat, roleplaying, and other challenges - will modify more rolls than any other ability.
That's only true if you lump the entire party's rolls together, which makes no sense unless everyone is forced to be the same race. For a comparison like this to be worth anything, you need to consider each attribute of each PC separately.
In an "average gaming session," a wizard will affect a vastly higher percentage of rolls with his Intelligence than with his Strength. (Many of those rolls will be made by the DM, for saving throws, but they still depend on the caster's attribute.) Ditto for a sorcerer's Charisma. Many times, the average session won't require a mage to use his Strength stat at all.
I played a sorcerer from level 1 up to 20, and over his entire career, he made perhaps a dozen rolls that required his Strength score. Most of those were checks to escape from grapples; ranks in Escape Artist would have made them unnecessary. He attacked in melee exactly three times, total, and never in a serious combat. Encumbrance was no issue because the strong PCs carried all the heavy loot. Giving this character a Strength bonus would have been of precisely zero benefit, but a Charisma hit would have been a serious drawback.
Long story short, the importance of every attribute depends on your character class. For some characters Strength is the most important; for others, it's the least important; usually it falls someplace in between. There simply is no universal formula.
When somebody wants to play some suboptimal race/class combination, I've got a house rule to make it easier. As long as they pick a Medium race of LA +0, they may remove all positive and negative attribute modifiers, and use exactly what the pointbuy generates. This makes the half-orc mage an unusual but viable character choice, rather than an intentional self-screwage.