Scrolling with mouse wheel, the default way

[Leledumbo]

I put a big TFrame descendant inside a TScrollBox, however when I scroll my mouse, nothing happened. So,
I override OnMouseWheel of the TScrollBox, and it works (but the redrawing has flickers).

The override was very simple:

(Sender as TScrollBox).ScrollBy(0,WheelDelta);

And I'm thinking, isn't it the default way applications use mouse wheel? So why can't this
be the default behavior (instead of nothing)?