If you are professional recruitment then why your company depends on third party (head hunter, HR consultancy) recruiter for hiring?

The first reason for hiring a third party for recruitment is the database of CVs. Which is their access to millions of candidates from different regions, specialities and expertise. A second reason could be that a third party will handle the screening and filtering process according to what the "Professional Recruiter" would request in terms of competencies, years of experience, mobility, etc. That alone, can save the "Professional Recruiter" a lot of time and effort.

The more option the better. Being a professional recruitment doesn't mean you don't need a little help from anyone, sometimes it is better if you have a lot of sources if there is a great need to fill up a missing positions.