From publisher blurb:
In Old School Games the role of reconnaissance is often filled by the thief. The problem is that while thieves are capable of reconnaissance, they are not trained for it. Their skill set is missing vital skills to be able to give the party good information on what lies ahead. To make matters worse the party must always guard their valuables when dealing with a thief. The solution is to get a person with a background as a military scout.
The Scout Class was created explicitly to fill the role of providing high quality reconnaissance to the party. In addition to this the characters military background means that they are more capable in combat then a thief of the same level. Finally, since they are not a thief the party does not have to worry about their valuables.