Just as a home isn't a home until you add furniture, the default installation of Ubuntu is fine for short-term use, but to really be usable over the longer term, it needs to be customized. Changing the background, sounds, fonts, buttons, and themes enables you to configure the desktop for whatever is best for you. For some users, static environments are best, but the user interface supports scripts that can dynamically change the desktop based on the current environment. Informative backgrounds, changing icons, smart menus, and adjustable fonts can really add to the system's usability and your own productivity.