Every succesful application evolves. Business logic is often one of the things that evolves the most, but it is customary to have data which changes over time. Sometimes - over months or years. A lot of spots have logic related to “data over time”. For example: you collect payments from users, but some users were not getting charged VAT. Your new users need to get charged VAT, but they will also pay more, but you want to “grandfather” your existing users into a pricing plan where VAT ...
