Quoting Adam Borowski <kilobyte@angband.pl>:
The en_US.UTF-8 locale has two purposes:
And I always wondered why other locales than en_DK.UTF-8 even exist!
• promoting C.UTF-8 in our user interfaces (allowing to select it in d-i,
making dpkg-reconfigure locales DTRT, making it the d-i default)
-- nice for Unix greybeards, but some users might want case-insensitive
sort, etc
If I had a beard, it were grey. +1