Example use cases: A customer has changed their name or address in the middle of the year, VAT number has remained the same. I created a new customer because I need to differentiate between before and after the change. Or another case: one of my customers has three invoicing addresses. I don't want a separate field "delivery address" on every invoice just for this exceptional case, I prefer to create three customers having the same VAT id and similar names differing only by some suffix between parentheses.