Sometimes they are systems problems. Static typing vs dynamic typing is a good example. The data you are dealing with may very well be dynamic in nature. You

Sometimes they are systems problems. Static typing vs dynamic typing is a good example. The data you are dealing with may very well be dynamic in nature. You could have a strongly typed entity for dealing with it, e.g. hashset, but you really gain nothing from it being strongly typed. You still have to check for missing keys and handle the dynamic nature of it. Using a dynamically typed language where everything is a hashset saves a lot of boilerplate code and can make the code easier to read. That's really what it's all about. Readable code. Different languages allow different levels of expression. You mention English as the business language that everyone speaks. Most programming languages can interface with C, and C has the largest ecosystem of libraries. Why don't we all just program in C? Because it's not very expressive. You used the words 'static', 'dynamic', and 'gradual' when discussing type systems. What if you couldn't use those words? What if you had to explain in painstaking detail what 'static' means because there wasn't a word for it? That's what it would be like if we all had to program in C.