One of the reasons for breaking code up into modules, (such as Alice primitive methods and functions), is to make them easily re-usable.
For example, the world object has a function named Math.sqrt.
That function can be called to compute and return the square root of a number.
The Alice development team were good enough to write that code for us and to provide it in the form of a standard Alice function.
As a result, whenever we need to compute the square root of a number, we don't need to "reinvent the wheel."