Identity columns are quite common in SQL databases. While the pros & cons of using identity columns vs GUIDs is a different topic all together, identity columns do make life easier if all you care about is creating a simple unique record identifier that increments automatically.
While this is easy and convenient what if you ever need to insert a value in the identity column e.g. while migrating data where original IDs need to be preserved. Simple, just enable insert_identity:
SET INSERT_IDENTITY [ClientTable] ON
insert into [ClientTable] (ClientID, Name) values (100, 'Company Inc')
SET INSERT_IDENTITY [ClientTable] OFF
Keep in mind that you can only override identity auto-generation one table at a time which is a bit cumbersome if there are many tables involved. Inserting a higher value than the current identity will reset it to use the current value.