The example the author gives is… frankly awful.

I can’t think of a single case where you’d want to remove the invoices of a customer you delete. Ever. In fact, the opposite is more likely to be a big problem, accidentally cascading your delete to your financial records!

Using a soft delete, your invoices won’t “disappear” because your app WILL have a view for looking at just the invoices.

Source: I built a bookkeeping system and soft deletes is a necessary feature.