Spaceship engineer: So, for mapping of the colonists' new planet I think we should equip the Covenant with PUPS. Those flying ball things that can build up a 3D map of an environment and detect toxins and lifeforms, amongst other things.
Company executive: No, sounds like a terrible idea. A little robot on wheels can do that in only a matter of months.
Spaceship engineer: Well, it's your call, but what if there's long grass? Or a wheat field or something?
Company executive: It can drive up on a hill, stupid!
Spaceship engineer: ...and the Covenant should have full interior coverage CCTV.
Company executive: Why? Just put a few cameras here and there. What you need is something to patrol the ship for unseen dangers.
Spaceship engineer: OK, you have a Walter android on board.
Company executive: No! Walter will be busy enough watching old movies and styling his hair. These are unseen dangers. Right then, the little robot on wheels. Ideal to find things lurking in the dark; in which case it had better be solar powered. Any questions?