Surely, HR departments, no matter if they consist of only one or fifty employees, can do the job themselves, however, other duties apart from hiring/recruiting, may halt the process, especially in the software development and tech industry in general. That's where recruitment agencies come up on stage who deal with fast and effective recruitment in a short time for the clients to save money and effort so companies can stay on the business track without getting super deep in the recruitment routine (by the way, that's us - hit here for an initial consultation).