Because a model alone can continue to be enriched with data many decades after its origin.
2005 - Designed in Revit Architecture
2012 - Visualized in Lumion
2019 - Enriched with IFC for Landscape
The same model enriched with more information and reused again and again.
The important thing is to start with BIM even though you do not currently have the expertise, features or functionality in software. This WILL come sometime in the near future. Without your BIM you can never start saving time and money from previous work.