So the unglamorous side of magic can include having to collect ingredients for the local magical powers. The higher up the migical hierarchy you are, the less likely it is you will collect your own eye of newt for use in a wide range of spells. Someone has to keep a record of the official spell books available (and know who has borrowed them!). If some witch asks you to look up a spell for this purpose or whatever, if you want to be able to get your pension at all, you will do as asked. And herbal ingredients don't collect themselves (unless you're really skilled at magic and are happy to waste magical power on a spell to achieve this when you could get some lowly paid minion to do it instead).
And the real thing about being a lowly paid minion that really grates? The fact everyone despises you. But someone has to be the lowest of the low even in a magical world. And that is the real function of being a lowly minion!