I know that more-dynamic-than-Java languages, like Python and Ruby, often allow you to place objects of mixed types in arrays, like so:

["hello", 120, ["world"]]

What I don't understand is why you would ever use a feature like this. If I want to store heterogenous data in Java, I'll usually create an object for it.

For example, say a User has int ID and String name. While I see that in Python/Ruby/PHP you could do something like this:

[["John Smith", 000], ["Smith John", 001], ...]

this seems a bit less safe/OO than creating a class User with attributes ID and name and then having your array:

[<User: name="John Smith", id=000>, <User: name="Smith John", id=001>, ...]

where those <User ...> things represent User objects.

Is there reason to use the former over the latter in languages that support it? Or is there some bigger reason to use heterogenous arrays?

N.B. I am not talking about arrays that include different objects that all implement the same interface or inherit from the same parent, e.g.:

class Square extends Shape
class Triangle extends Shape
[new Square(), new Triangle()]

because that is, to the programmer at least, still a homogenous array as you'll be doing the same thing with each shape (e.g., calling the draw() method), only the methods commonly defined between the two.