The usecase for vocabulary would be - in my specific case for spells, places and names that - as it is a fantasy game - might differ a bit from normal words that the software would know form a dictionary. But I could imagine a broader usecase, when there are specific industry terms that get thrown around in meetings. At my lawfirm from the top of my head I would know some words/acronyms we use, that are not used in the broad public and I can only assume that for engineers and other more specialised industries this might be even more of a case.
