A table you first have to create it.
Then you can alter it.
But in a development/test/production environment this is not always practical.
Since you may want to change something of a new table before it goes to production.
You can use PL/SQL to avoid installation errors:
If the table doesn't exists, then do create.
If it does exits, then do an alter.
It makes a table script more complex.
So it would make our developers life much easier if it was possible to have the table syntax:
create or replace table XXXX
(...);