As Laravel documantation mentioned for DB class method insertGetId:
When using PostgreSQL the insertGetId method expects the auto-incrementing column to be named id. If you would like to retrieve the ID from a different "sequence", you may pass the column name as the second parameter to the insertGetId method.
In context of code, returned ID's isn't used, we don't need it.
As Laravel documantation mentioned for DB class method insertGetId:
When using PostgreSQL the insertGetId method expects the auto-incrementing column to be named id. If you would like to retrieve the ID from a different "sequence", you may pass the column name as the second parameter to the insertGetId method.
In context of code, returned ID's isn't used, we don't need it.