I'm thinking that Rio's EH's serve more of a 'companionship' function rather than him actually needing them to fix the ship.Do you really need a navigation hologram? The ship's computer runs the navigation and drive systems and the holograms, so does it make sense for the computer to run a hologram program to push buttons on a console when the computer could just cut out the middle man and do the navigating itself?
Though if one can just holler out, "Hey Ship, Fix That..." and then sit down to read a book for a couple of hours, I can see the advantages.
