Closing a window

[bgold]

Hey, I have a rather useless question, but I'm bored so I'm asking it.

Why are there so many ways to close a window? There's:
(1) Click the x.
(2) Double-click the icon.
(3) Right-click the icon (or taskbar button) and click close (also,
pressing alt-spacebar-c when the window is active has the same
effect).
(4) Press alt-F4 when the window is active.
(5) Press ctrl-w when the window is active.

And there could be more ways I don't know about. What's the deal with
that?