Why would guys follow me and then unfollow me?

My account is private. I don't post much often and rarely post picture of myself. I just share memes. I don't get it what's point of following and then unfollowing. I would understand it if it was by some teen who wants follower. But it's from mature adults with same profession as mine. . I find this behaviour really immature and annoying.
Why would guys follow me and then unfollow me?
Post Opinion