CiviEvent registration with payment doesn't create associated Contribution

When entering an event, with payment, via the backoffice, no contribution record is created.

It happens when I record the event either of two ways:

1. From contact page, click "events" then "add event registration" then record the event & payment

2. From Events menu, select "record event payment" then enter contact & payment info.

In both cases the event is recorded, entries are made in the line item table, but no entry in the civicrm_participant_payment table and but no contribution is recorded.

By contrast, if I record a credit card transaction (same as #1 above but on the contact page click "submit credit card event registration" then a contribution record IS created. Also if a user registers for an event using the event registration page, a contribution record is created. So only the two backoffice registration methods outlined above fail to create the contribution record.

I verified this behavior is the same on the current drupal demo site--no contribution record created.