To start with, the term headhunter is one of the oldest terms used in the recruiting industry and can be applied to a single-shingle recruiter or individuals within a larger firm whether they are contingency recruiters or retained search consultants.
Contingent search and their recruiters are generally driven and measured by numbers and not necessarily quality. That is the number of dials, connections, candidate phone interviews, candidate submissions to their client, client/candidate phone interviews, client/candidate onsite interviews, client/ candidate final interviews, etc.
One way to describe contingent search is that it is a race to see which of their recruiters can find the most candidates first to win ownership of the most candidates. Why the rush? Because they are not only competing against their own internal recruiting team to email/connect with candidates, but they are also competing with other contingent firms.
Additionally, some contingent firms stop working on roles that become stale or have an undesirable hiring manager, etc. and they will not tell their client they have stopped working on their role. They move on to the lowest hanging fruit of the typically 30+ searches they are working on concurrently. This behavior is driven by the environment that their clients have created, because they would rather work on something that has a greater likelihood of success with the least amount of work.
There are two key criteria that sets retained search firms apart from contingency search firms, which is coupling a retainer and exclusivity on a search. A signed engagement letter provides the retained search consultant with the client’s commitment to get a role filled and removes any conflicts of interest along the way. It also creates a more trusted advisor relationship between the hiring manager and the search firm.