Yes, int based classes do well in the skill department. A wizard ends up with as many skill points as a rogue after a while.
One thing to note, though, is that the rogue gets a much better selection of class skills. That give him an additional +3 in those skills over a wizard.
Intelligent characters already get extra skill ranks. Every level you get (class skill points) + Int.
The reasoning is that the average Wizard is going to be spending his days studying magic, not listening at doors, sweet-talking people, swimming, or practicing his horsemanship.
A Rogue, on the other hand, spends almost all his time practicing these kinds of skills. He's not as smart, but has a lot more practice.
RumpinRufus has it. It's kind of based on how much time a given class would typically spend on skills.
Wizards and most spellcasters spend the majority of their time focused on--what else?--magic. Learning spells, learning how to cast spells, learning the theory behind the spells. Sure, they might read some books and learn about history or the planes, but for the most part, they focus on magic.
Fighters and warrior-types tend to spend most of their time on combat. Learning how to effectively decapitate/shishkebab/bludgeon a foe takes time. What they don't spend on this is spent learning to ride, or building muscle to climb or swim even in armor, or getting your "mean face" to be scary enough.
Rogues and skillful types, though, they spend the majority of their time practicing skills, because that's what they're meant to do. The rogue doesn't need to pore over musty old books, or learn just where to grip that obnoxiously big sword (how could anyone hope to move around with that thing on their back?). Instead, he/she learns how to pick locks, how to tread softly, how to get worm your way out when that lock jams and you're not as quiet as you should have been. And, when all else fails, the best place for a cheap shot so you can get out.
But yeah, Intelligence helps anybody. Really, most classes have a few skills at which they excel, and it's rare to have a true Jack-of-All-Trades doing everything for you (for one thing, that'd be crazy MAD).