The fact that sub-menus don't support icons.
http://developer.android.com/intl/fr/guide/topics/ui/menus.html
<http://developer.android.com/intl/fr/guide/topics/ui/menus.html> *Icon Menu
* This is the collection of items initially visible at the bottom of the
screen at the press of the MENU key. It supports a maximum of six menu
items. *These are the only menu items that support icons* and the only menu
items that *do not* support checkboxes or radio buttons.
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