Every package is a chain of confirmations. A hotel, a restaurant, a guide and a transfer each confirm separately, and one unconfirmed link is a weekend that collapses on a Friday afternoon.
The margin lives in the rates. Negotiated prices differ per supplier and per season, so knowing what each component actually costs is the only way to tell which package is worth selling.
Failures land on you. When a restaurant closes or a guide falls ill, the customer holds you responsible, so having a second option recorded for every component is what turns a disaster into an adjustment.
The good rooms go early. Blocking allocation with suppliers months ahead is what allows a package to be sold at all in high season, and it commits money before anybody has bought anything.