Are there specific needs for these statements to be divided into groups, or is this done to logically term the various types of statements (in discussions, reference documentation, etc.)?
Are there use cases where it would be important to segregate these statements into these sub groupings?
These are classifications, they exits for the same reason every other classification on anything else exists…
Regarding use cases, I hardly see a situation where you would use those terms but maybe if you are the Business Analyst for a SQL Server management tool you could say that you dont want users to have access to any sort of DDL statments, meaning the users cant create objects on the DB…