Currently, the SQL privileges (SELECT, INSERT, UPDATE, DELETE) are managed at the tables level, which can be very tedious when you have to administer many roles in an organization, and need to keep them sync with a constantly evolving data models.
By managing privileges at the schemas level, will allow to give SELECT and other DML privileges to *all* or *several schemas* to a role|user, fixing the need to manually synchronize the new tables|views to the roles.