Feedback and improvement
I don’t like resumes. When conducting my job search, I had to build my resume and sent it in for many different job openings. I really did not get much response for all of these applications. I liked my resume well enough, but I could not be sure how hiring managers saw it. I never had a chance to get that feedback. I could never really improve it beyond a certain level because I did not know what appealed to hiring managers.
It is hard to improve in a vacuum. Feedback is the key to finding opportunities for improvement.
As an aside my resume was not especially important in getting my current job. I was a contract to hire. My resume was submitted by a staffing agency and picked up for contract. My body of work during my contract earned me my full time job. One of the last things my manager asked me for during my transition to full time was my resume. He had never seen it.