I use turtle pretty often in a teaching setting. It's extremely common that I'll define the following function at the top of my code:

def teleport(x, y):
    turtle.penup()
    turtle.setpos(x, y)
    turtle.pendown()

Shouldn't this sort of method already exist within the turtle class?

In my view, turtle is a great tool for exploring _polar_ coordinates. If you set emphasis to rectangular coordinates, there are many tools that are much better.

Second, your function might be ok for you, but it is really not suitable for standard library. Probably you meant something like (a method)

    def teleport(self, *args):
        restore = self.isdown()
        self.penup()
        self.setpos(*args)
        if restore: self.pendown()

What other Turtle implementations support the teleport command?

Turtle is  the most accessible and well-known drawing module for kids to use so teleporting makes more sense in the context of drawing random shapes or small pictures around the screen. I've seen the penup/goto/pendown combo so often that I figure it at least warrants a suggestion. Also my crappy function was mostly just meant as an outline, haha.