10000 tables under one roof are by no means a large number.

Well designed, normalized handcrafted schemas can have hundreds of tables (many basic datatypes, many entities with a few many to many relations each).

Then mechanisms that create and copy tables automatically (e.g. by time intervals; to segregate versions or epochs or instances of something important; as snapshots or temporary duplicates or backups) can easily increase table count by two or more orders of magnitude.