Sure, for the first 10% of the lifetime of a system. When you are starting, the schema is simple, there aren't a lot of special cases or bad abstractions, and

Sure, for the first 10% of the lifetime of a system. When you are starting, the schema is simple, there aren't a lot of special cases or bad abstractions, and things are easy. 10 years later, there are special cases on top of the special cases. The reality of compromising over and over when adding new features has added up and it's hard to remember the right way to get the correct currency converted total for an invoice (so you need to get the total in each currency, but not add the line items that are marked as 'deleted', then apply discounts, then convert currencies to USD, then add tax, then add shipping, then convert to the local currency, except when the delivery address is in Russia where legally you have to ...). Lots and lots of things are like this, and with no abstraction to ensure that these computations are isolated in a single component in the system you are going to get nowhere.