I worked as a consultant with a phone operator who were insourcing their inhouse sales (telemarketing) after having it outsourced. What they had discovered was that by outsourcing that function they had lost a large chunk of their overall talent pool that they could recruit from to almost any other function (especially sales of course).
A past company I worked for decided to outsource recruitment.
Went from having a dedicated human to talk to knowing me, and being aware of what kind of team people were running to having generic folks on the phone crawling linkedin profiles for me.
Who do you think was having a better success rate at finding the right candidate?
In companies where there are many roles open, someone needs to be aware of what kind of team would fit the profile to ensure success.
A couple years later, half the teams were using under the radar private hiring firms to help find talents.