I have absolutely no idea why it happens. It just happens.
From time to time, QTP seems to lose or forget its menu configuration, leaving the user with a very limited amount of options. See examples below.
Workaround: fortunately for us, there a very simple way to make QTP put its menu configurations back in place, where it should never had left.
Right-click anywhere in the menu/buttons area and select Customize.
Next, I recommend you to close down and restart QTP. Never knows.