Having lots of staff members doesn't give a Discord server the ability to easily just temp mute or ban someone. Things like this are one of the core purposes of Discord bots.
Plus, just because staff can deal with it themselves, auto-punishments just make their lives easier. Sure, they can deal with it as is but why would anyone say no to making their lives easier?
A Discord bot for moderation has been something I've been asking for for literally years, and has been continually refused. As much as it's insanely useful, Cube refuse to add one and never really specifiy a proper reason. There may be some moderation features setup with Discord bots when Cubecraft releases passport, but from the sounds of it the only purpose of this Discord bot is for verifying people to get onto the Discord server.