Otherwise it breaks peoples rhythm or causes accidents. Once again, you can drop the 'alt' for the second character. Also, once again, you can use the arrow keys to move the selection down until you get over the close, and press return, in only 5 or 6 steps. Or try to train themselves and have all these bad choices. It is like wanted to get from point A to point B and always having to traverse a maze with lots of dead-ends, or winding paths that may eventually get you where you are going, if you hack at it long enough.
Windows also use the corners and edges to resize the window.
The close kill is very close to that, causing other accidents. Because of all the potential for error, this forces users to move much slower when doing things to avoid surprises. Ask windows users about this, and they admit that they move slower and more carefully to avoid this problem. Think of the productivity wasted. Apple wisely places close and zoom on opposite sides of the window to avoid such errors.