I've seen lots of exos in the tower with serving jobs like being a post person, cleaning, or being a guide. I feel like this is the proper role for all exos as I don't think they are very adept in combat. Whenever I see exos in the crucible I feel like I should destroy their ghost as well so I can dismantle the exo and use their parts to upgrade my weapons.
Those are robots in the tower you are referring to, not Exos. Exos are sentient killing machines, created for war. They are so complex that no one understands how they work, not even themselves or Ghosts.