Well, let's say you were looking for a piece of information in a modern day campaign, and the GM sets the difficulty for the Contacts roll at 4. Since it's a modern campaign, things like being in a different town aren't going to add to the difficulty of the roll--distance isn't much of a factor with cars and cell phones and the like.
But turn the clock back 150 years or so, and reaching that same piece of information has more factors affecting the difficulty. You can't look up his contact information in the phone book, and even if you do know where he is, it's going to take time to get there.
So those added difficulty factors would ratchet up the target of the roll to 8--meaning that your average gadfly is going to have a tough time ferreting out someone nearby who knows the info. So a roll of 5 might be interpreted as him spending a day talking to his acquaintances about who might know the answer, and two more days actually going to find and talk to this person.
But a wizard, who can make maneuvers from magic, just straight up call a demon to ask, or just take a stroll through the Nevernever to turn a two-day trip into a 20 minute one, would have an easier time meeting that difficulty directly, and therefore get the answer more quickly.