Why does Excel capture mouse wheel events when it has the focus but the mouse isn't over it?

In modern Windows applications, mousewheel events are delivered to and responded to by whichever application the mouse pointer is over, even if that application doesn't have the focus. For example, I'm typing this post in my web browser, but if I mouse over the instance of Notepad++ open on my other monitor, and use the scroll wheel, Notepad++ scrolls even though it doesn't have the focus. Microsoft Excel doesn't work like this. If Excel doesn't have the focus and you hover the mouse over it and scroll the wheel, it doesn't scroll. Worse than this, if Excel does have focus and you mouse over s

Question by Hammerite on Super User, licensed CC BY-SA. We show a short excerpt and link to the original thread as credit.