Some possibilities I imagine:
*We (think we) know that Arcana, Religion, and History are skills in the game, even though they're not on the Rogue class skills list. These would all seem likely to be Int-based. My guess is that Int is a secondary stat for warlords, warlocks and clerics, playing into their powers the same way Charisma and Strength play into the rogue's powers... so in other words, Int would be a dump stat for rogues, but not for several other classes.
*Even if Intelligence doesn't directly affect your skills, it may be extensible through feats. For example: "Jack of All Trades (Requires Int 14): You add half your Intelligence bonus (rounded down) to all untrained skill checks."
*This might be an intentional design decision: make each class depended on one primary stat, with a couple stats of secondary importance, and one or two "dump stats." (Wizards would dump Str, Clerics might dump Con, and so on.) As long as the dump stats differ per class, this might lead to more interesting variations in party makeup. (Rather than having a party full of ugly guys, you have one ugly guy, one stupid guy, one feeble guy, etc.)