Do you mean why something changed from a business perspective or from a logical perspective? Using Lookup and Conditional Split transforms it's quite easy to track whether column values have been Inserted, Updated or Deleted and then you could populate a 'ReasonForChange' column accordingly. If it's the business reason for change that you want to capture, that would likely need to come from the source system, otherwise you'd just be guessing I'd have thought.

Regards

Lempster