If you use database replication definition and subscription in a heterogeneous environment, you do not need to use a table replication definition.
In a replication environment involving databases with many tables, maintaining all the table replication definitions requires more effort. During DDL replication, if the DDL changes the table definition without coordinating the changes with the table replication definition, the data might become inconsistent. To avoid data inconsistency and to eliminate the need to use table replication definition for each table, you can use database replication definition and subscription.