I don't think having well-defined precision is a rare requirement, it's more that most devs don't understand (and/or care) about the pitfalls of incurracy, because they usually aren't obvious. Also, languages like JavaScript make it hard to do things the right way. When I was working on an old PHP codebase, I ran into a popular currency library (Zend Currency) that used floats for handling money, which I'm sure works fine up until the point the accountants call you up asking why they can't balance the books. The "right way" was to use the bcmath extension, which was a huge pain.