the interest in vector database rise as an external, specialized service in a system that runs in addition to the "single source of truth" data lake where the data actually resides.
like Redis and Memcached before, it solves a specific problem. Redis started to act like a fully fledged DB (with weird persistency method and guarantees) only after it was really wide-spread.
sure, every DB will support vector and every vector search engine will act like a DB. But that's missing the point that vector search is an expensive problem with tradoffs that justify a specialized design
btw I'm working in a DB startup - https://hyper-space.io/