(The substring part of it, not the locale-sensitive part.)
Perhaps because english is all it matters to them. Who in Europe, for example, even cares if a forum or chat has some swear words in his language?
We might be even more pissed off that we can't swear and leave the service, rather than complain about it.
http://www.dailymotion.com/video/x98y4u_eminem-interview-on-...
It's at 2:30 where he talks about it. And swears a "little".
When I watch Misfits (UK show) they say some things that I never hear on American shows. It only happens on shows that are after the watershed[1] though. Before then I don't know which parts are censored.
It always amuses me a little how Americans seem to be more strict than the Europeans for media censoring.
There's a blog post on it here: http://blogs.msdn.com/b/michkap/archive/2010/12/04/10100294....