The key differentiator between a self-managed schema create file and Liquibase (or other schema migration tools) is that the latter provides a schema changelog. This is a record of the schema changes over time. It allows the database designer to specify changes in schema & enables programmatic upgrade or downgrade of the schema on demand.
There are other benefits, such as:
- Database vendor independence (this is questionable, but they try)
- automated documentation
- database schema diffs
One alternative tool is flyway.
You would choose to use a schema migration tool when you want or need to automatically manage schema updates without losing data. That is, you expect the schema to change after your system has been deployed to a long-lived environment such as a customer site or stable test environment.