@onionsoup probably because static methods are a bit of a code smell in an OO language. They are much better represented by top-level functions in FP and the companion object is merely a way of grouping these functions.

andyb: well but the result is the same. you have a bunch of methods inside a class and you call them using the class name. if the static methods were a code smell then why aren't the companion object's methods a code smell?

Because companion objects are real objects. Static methods do not belong to any object. Companion objects are singleton objects attached to a class.

It also provides a cleaner separation from the instance properties on the class.