Liferay includes support for many languages thanks to the translations of many contributors. Up to now all these languages are enabled by default which has two problems:
1) Having so many languages enabled causes usability issues for fields that can be translated. In a real installation there will most probably never be so many languages enabled
2) Since not all translations have the same quality it produces a mixed impression of the product. By focusing on the 7 supported (aka non-beta) languages the impression will be improved.
System Administrators will still be able to set their preferred languages to be enabled by default setting the locales.enabled propery
Developers will be able to do the same through a hook that overrides that property
Portal Administrators will be able to change the languages enabled through Control Panel > Portal Settings > Display Settings