Some of my observations from technical translations:
1) more often than not, they seem badly translated, or there just isn't
useful local Language terminology which would be commonly understood.
2) technical folks don't even know what the local Language term X refers
to (compared to the English version), as the terms aren't stable, and
globally common. So, using the local language is often a much bigger
problem, especially if you report bugs, discuss features or such in
English.
3) translations are often not really in sync with the latest versions,
some translations are missing, or not everything is translated anyway.
You're right ! But those problems are _nothing_ compared to the problems
you face when you don't speak a single word of English and yet have to
use English-only apps.
I really think a bad translation is better than no translation at all.
Even if I prefer running my desktop in English anyway (I'm a native
French speaker)...