It is just a personal perference. Imagine I have a database for my application already and I also need one for SpiceDb. At the moment, I can either 1. have two isolated databases, my_app and spice_db 2. use one database, my_app and all tables generated by spicedb are under my_app too, but it is a bit messy, especially

metadata

is quite generic. WIth the help of schema, all tables from spicedb are grouped by the schema and easier to manage.