[IronDragon]

Flipping to the back of the SoA Game manual:

Thieving skills are adjusted both by dexterity and the type of armor worn while making the attempt.

For example your thief with 18 Dex and wearing studded leather had a total of 85 points in pick pocket ability. Her Dex score will add 10% to the success roll while the armor will remove trying to pick pockets while wearing studded leather earns you a -30% to your roll. Meaning chance of success in 65%. Loose the studded armor and her chance of success soars to 95%.

The reason to have more than 100 points in any skill area is to compensate for armor worn.