Version control is a big one for financial institutions, because there's no way to verify what the state of a spreadsheet was when a particular analysis was done.
One place I worked at created a Python library called the DAG (Directed Acyclic Graph) for this. It enabled an easy way to translate a chain of Excel cell functions into Python code, which can then be version controlled, diffed, code reviewed, etc.
Or until a spreadsheet is edited in Excel that uses language other than English - formula functions will also take nationalised names.
Or until multiple people make changes to a spreadsheet, but there is no version control in Excel.