Should a CEO serve as a mentor to their management team?

I started mentoring both senior and junior leadership talent a number of years ago; and I have to say it has been one of the most personally and professionally rewarding experiences in my business career.  If we will take just one person at a time and invest in them, it is amazing the number of lives we can impact throughout our career. It can be within or outside the organization. Having done it for a while, I now find I have the time to work with up to 2 to 4 people because it becomes effortless. If I go through a difficult time, and find myself not willing to give something back, generally, I have found I learned the wrong lesson. 

As an opposing view, does mentoring facilitate growth in an organization? Or does mentoring undermine our ability to lead.  If we befriend a subordinate, can we do our job as the CEO?  At times, it can make your job more difficult, but I have found the rewards outweigh the risks. Further, there is no prep required, just show up, listen, and advise only when needed.

I would love to get your thoughts and experiences with mentoring. It has helped me to find joy and greater purpose in my work, which helps me avoid burnout from a demanding schedule.