'Default' is not inserting values while creating tables.

Question

The table has been created through the query below

CREATE TABLE customer
(First_Name char(50),
Last_Name char(50),
Address char(50) default 'Unknown',
City char(50) default 'Karachi',
Country char(25),
Birth_Date date)

but the default value is not inserting values in their respective columns, what's wrong with the query?