I was a SWE for a large corp for a while, and after that transitioned to a role of manager.
As I was very eager to build a good team, and the company HR looked slow and unefficient I tried doing recruting myself, at least the part of meeting people and talking them into come to work for us.
What I could decide (up to a point) the salary and benefits but people had to go thru testing with the people from HR (IQ tests, personality tests etc)
Anyway I was pretty successful in finding experienced engineers but the thing fell apart when it came to HR testing. "He/She is not a good fit for the company" they would told me.
This was going on for months. I did more than 300 interviews in my free time in maybe 5 months and only about 5 people where "ok".
At some point a guy from HR told me: 'you must stop sending employees from companies X,Y,Z to testing, we have a deal with them that we don't take each other's people' 0.o
The deal was not only no to stop "poaching" but when someone form those companies applied to a job posting they would call up the other companies HR and told them about it.
And there was more than 10 of companies they told me about that where forbidden.
Imagine all the people that applied for job at some company not knowing that their boss, the HR etc. would know about it.