Business Use Case: You may be doing peer-to-peer fundraising using a 3rd party tool and have an exported list of donations you wish to import into Salesforce. You also wish to track who the Fundraiser was and attribute it using the Salesforce NPSP standard soft credit functionality.
This means that you need to have a separate CSV file per soft credit person/fundraiser.
You will need to create the fundraiser as a contact in Salesforce (if they don't already exist).
On the Import of each csv file, you can specify in ProntoDI which person to attribute the Soft Credit to, and what Contact Role they have e.g Influencer.