Because working with people you like makes work so much more bearable? We have an AP lady who is a hotshot, does such a good job but so mean and hotheaded and thinks she is “honest” but is really just mean. Hates her husband , hates people, only likes her dog. Her manager is on her last straw because she criticizes everyone else all the time and dislikes half the people she works with, and she (the manager) has had to referee arguments she has with the rest of the staff.

You can train someone to do a job, it’s much harder to train someone out of being an asshole.