For the same reason that french teenagers ( and olders) find "porn" on google, even when they don't speak english.
See, universal term !
And that's not even the point.
If you don't want french, italian and spanish sections just because you don't understand it, it's your right, but i think we are far away from an invasion.
I don't think it will screw the english nature of the site.
It's just a plus, but you obviously don't want to share.