Ubuntu and language packs

[Surfaz Gemon Meme]

Well, Spanish support of Ubuntu is not full and if I uninstall all
English packages (I always do it), I don't have any problem.

If there is something untranslated to Spanish, Ubuntu shows me in English.

I am not a developer but, I think that almost 100% packages of Ubuntu
CD use gettext library for internationalization.

Gettext system works with .po files in source (mo and gmo in binary).
I translate some programs in my free time, and I think I know more or
less how is a .po file. In each file there is a copy of the original
language (English) and then a space that is used by programs like
poEdit for allow put your translation into your language.

1º There is a copy of original language in every translation
2º Gettex takes strings of programs, therefore system always can use a language.

Please, someone can answer me what if there is any reason to do this
or is simply a mistake?