Advantages of Identity Columns
The main advantage of an identity column is its ease of use in defining a unique row identity value. An identity column guarantees row uniqueness in a table when the column is defined as a GENERATED ALWAYS column with NO CYCLE allowed.
It might be difficult with some tables to find a combination of columns that make a row unique. If a composite index is not desirable for the table, you can define an identity column as the primary index for the table.
An identity column is also suited for generating unique primary key values used as employee numbers, order numbers, item numbers, and the like. In this way, you can get a uniqueness guarantee without the performance overhead of specifying a UNIQUE constraint.