20 years ago, when the vast majority of computer users wrote in a latin alphabet-based language (and that virtually everyone of them always used the same language), this wasn't much of an issue.
Now, there are more and more reasons to demand the following :

// Being able to use a computer in an arbitrary number of languages AT THE SAME TIME
(OS language, spellcheck, INPUT, web browsing..)

This means :
** excellent Unicode support
** easy installation of input methods for 'exotic' (not exotic for everyone !) languages, and making sure you can switch between them easily. I'm not only talking about keyboard layout here (think asian languages, etc..)
** no encoding issues when writing and reading offline and online documents
** automatic installation of the correct truetype and console fonts

Reasons :
-Billions of people speak a language not written in a Latin alphabet
-More and more people learn and use many languages
-More and more people talk to and write emails to friends who understand different languages

Failure to implement this correctly in a user-friendly distribution severely limits its ability to be widely adopted (think India that has tens of official languages and where most people speak several of them ; North Africa where businessmen are likely to write in Arabic, French, English, and soon Chinese..).