With 3 other facinating large moons in orbit around Jupiter, asking for yet another in Callisto would have been expecting too much. This body is one of the most heavily cratered bodies we have yet seen. The heavy cratering record tells us that little has changed here on Callisto since early in the solar system’s history. So, not unlike our moon, not very much happens here… ever.
Although there are some theories being floated that Europa may not be alone in its candidacy for an internal ocean of water. Some think that Ganymede and even Callisto may also host such environments but to a lesser degree.