[CentOS] C6: why i686 are installed on x86_64 based arch?

Tue Sep 9 07:10:29 UTC 2014
Mihamina Rakotomandimby <mihamina.rakotomandimby at rktmb.org>

Hi all,

I noticed that when I install some packages (precise list not defined), 
my x86_64 C6 tends to install both 32bits and 64bits at the same time:

# yum install fontconfig freetype \
               libfreetype.so.6 libfontconfig.so.1 \

Gives: http://pastebin.com/FNzztefV
My repository configuration is same: http://pastebin.com/Hf38sAic
No 3rd party repository.

No i686 initially installed:
# rpm -aq | grep -Ev '(noarch|x86_64)'

I dont want that, unless I'ts really mandatory: Is it?
One solution would be to append the architecture to the package name to 
install, but how to make it default, in order to save typing?

Thank you.