1. They are having trouble finding great candidates. If an organization is serious about finding great candidates and getting those positions filled, they may outsource their recruiting to source candidates in more places, to improve their employment branding, and/or work on the job descriptions for these positions.
2. It takes time and resources away from the core business. This is especially true for smaller companies, who might not necessarily have someone on staff to just work on recruiting.
Outsourcing recruiting helps them by allowing them a consultant to do what they do best without taking away from what the rest of the company does best.
3. They need to reduce their turnover rates. A high turnover rate can hurt a company's bottom line. This is often a sign that there a bigger problems with the company's recruiting functions, problems that are not necessarily fixed by increasing the salary or by doing a better job interviewing.
4. It levels out the playing field. Start-ups and smaller companies will outsource their recruiting function because they don't have the resources in-house to keep up with larger companies.
By outsourcing, they can level the playing field and not have to worry about losing good talent because the larger competitor did a better job of selling the position or offering benefits.
5. They need to cut costs. Companies outsource recruiting to reduce their costs, whether that's labor costs, capital costs or perhaps costs from the previous reasons. Also, perhaps the organization didn't do a good job of creating a standardized approach to hiring so outsourcing will provide the organization needed.