The term "reaper" is used generically, and anyone can be a reaper as long as they can find an Enfant with a caul. However, reaping is an important economic and social activity in wraithly society, and many reapers operate under either governmental aegis or the equivalent of a privateer's license.
Reaping is a profession open to corruption; while many reapers are at least moderately well-disposed towards their charges, a significant fraction are slave drivers. An Enfant may find their caul cut, only to become a Thrall in chains and immediately marched off to the forges. Alternatively, since Reapers often are the first source of information an Enfant has on the underworld, they have a golden opportunity to color the Enfant's point of view and outlook - whether that be Transcendence, Charon's dream or the complete destruction of the Iron Hills. Most wraithly organizations sponsor reapers as a combination of midwife, indoctrinator and tax-farmer in order to expand their own power.
For example, the Emerald Legion is used to dealing in mass Shroud-crossings. As the victims of happenstance, they may acquire a dozen or more Enfants when a plane crash occurs. As a result, the Legion employs full-fledged reaping squadrons who will work as a team to bring in a new cadre of Enfants for recruitment and indoctrination. Independent Reapers cannot rely on such support, and often survive through a combination of wits, Fatalism and whatever relics they can take off of their charges.
In contrast, the society of the Yellow Springs depends heavily on White Jade and the smelting of souls. To that end, Yu Huang effectively tax farms out reaping duties in the conquered territories. Under this arrangement, families bid for how many souls they will deliver to Yu Huang, and then can pocket the difference themselves. The result is that most non-Chinese Asian wraiths are lucky if they escape conversion to White Jade.