They actually are, but the interfaces are designed so that you shouldn't need to use the menu at all if you know the operation. Instead, use an assigned shortcut key.
That's another reason why it doesn't really matter that the menubar is at the top, even if you have : essentially all the menu items you'd want to use frequently are assigned shortcuts. And if you use it frequently, you'll remember that shortcut.
(BTW: the secret key to move focus to the menubar is Control-F2 by default; you can find and/or change it in the "Keyboard Shortcuts" item in System Preferences. Once the focus is on the menubar, by pressing that key or by clicking, you can move around with the cursor keys.)