There are a lot of reasons...

The biggest one is: beeing forgotten.

Or for example, when one database comes from a completely different server but the login is beeing used by more...

i added the update one for users that have a different Id than the login on the server.

 INSERT INTO ##tbl_db_principals_statements (stmt, result_order)
   SELECT ...

what if the users own things?

I just added the "EXEC sp_change_users_login 'Update_One', 'login', 'user'" to the creating of the users in the script. If the user is already mapped it does not raise an error....

i ve modified it so that

-i get the results in a table before i restore my DB (modified a little the skript of S.Gusen)

-restore the DB

-then i change all owners...

Skript is amazing... Using it all the time...

Does anyone know if the same exists for removing Users? I want to remove the users that left are in the Backupfile