Our moon is crucial for Earth's life because of its relatively large size. It stabilizes Earth's rotation and provides a tide cycle. Both of which are crucial for life in terms of stability.

Jupiter and all the other gas giants have so many because they're more like remnants of their creation. Not much different than the asteroid belts. Just spare parts so to speak from the formation of the planets. So they don't do much for life. Not to mention the environment around Jupiter is incredibly hostile so even if the moons were providing something its too an extreme an environment.

Under the surface of the major moon however, well.. that's a different story.