Hirelings of all sorts are so important to the game that even many of the earliest RPG rulebooks had listings of the types available and average pay. As a GM, you know there are all sorts of reasons your players might need hirelings -- they decide they want a local guide, for instance, or they need to hire some guards for those large, awkward items they hauled out of the ogre "king's" lair. As a good GM, you want to have more than just a list of stats; in fact, you know it's more interesting to have two NPCs with identical stats but different personalities than it is to have two with the same (non-existent) personality but different stats.
That's where 1001 Hopeful Hirelings comes in. Here you have a thousand possible hirelings, some good and faithful, some disloyal, some just plain crazy. They're all different, and all interesting. The little details about them, with a moment's thought, can come together to supply a character background. Why does the former poet have a death wish? (given that he's a poet, probably unrequited love) What did the laborer do that he seeks to atone for, and does that have anything to do with his nightmares? These 1001 NPCs are just waiting for you to tell their stories.