I have a young relative who is "friends" with a huge (to me) group of friends from high school, his church when growing up, Boy Scouts, college, and previous work experiences. This is especially true if these "friends" are socially elite or have been successful. Something he learned (?) early on about "contacts" and "networks". Don't know how much that has helped his career but it has done a lot for his social life.
All that said, it seems that coaches who desire to stay in the profession tend to make as many "friends" as possible. Never know when you will be either looking for a new job or for an assistant. Definitly easier to keep in contact with today's social media. I am acquainted a high school coach who keeps in regular contact with dozens of "friends" he has made in the profession. Never know when you will need them.