Today I was watching Sherlock Holmes and The Game of Shadows. In that movie, several foreign languages like German, French etc. were used. The film itself had no translation in English despite some small elements. Some conversations were inaudible too. I do not mean those inaudible words cannot be guessed, but why is it done so? I have a feeling that they made such things (not showing translation in English, inaudible voices) intentionally and these are not errors. But I cannot understand how this technique can add value to the quality of any movie? Does anybody have explanations?
I didn't know about Sherlock Holmes case, so I am answering it in general way.
If it is unintentional then it's movie mistake but if it's done intentionally then it can be due to various reasons
To hide Spoiler- sometimes it's done intentionally to add inaudible dialogue or foreign languages to hide the spoiler in a movie which may end up ruining the climax for the audience.
For hilarious effect- Sometimes it's for adding Humor as in the case of Luis Bunuel's The Phantom of Liberty. (source)
To reduce redundancy- If the same sequence of event and dialogue is there in the movie then sometimes redundancy of dialogue is also reduced by using inaudible dialogue. Example- About two-thirds of the way through North By Northwest, the Professor explains the whole "George Kaplan" scenario to Thornhill at the airport, and his voice is drowned out by the roar of plane engines. This is actually done to reduce redundancy.
In case of a foreign language, it is also used to present the events from the point of view of a certain character who doesn't speak the language, and thus does not understand it.
Sometimes some dialogues are not so important, so they may make it inaudible.
Sometimes it's also done to shorten the long conversation.
Some similar examples are given here.
In most movies that I've seen, and certainly in The Game of Shadows, there is enough context to have a good idea what is being said. In some movies there is a brief phrase. (I remember one in Arabic: احضرهم), meaning "get them" from the villain to his henchman. When the location of someone is revealed to the antagonist, and he turns and says something, causing his henchman to run away, you know it means an instruction to go mobilize. It gives a little more flavor to the movie without detracting from the understanding.
Evette from Clue says, "oui!" and there are a million other examples. This adds a tiny bit to their character ('French Maid') besides just an accent.
Indiana Jones & the Last Crusade has Indy pretending on a blimp to be a ticket taker going down the rows asking, "Fahrkarte, bitte" over and over - you know he's asking for tickets in German; no need for a translation, but it is part of the plot.
Bonus: Cuss Words
I've heard "sheiße!" many times in a movie. You can maybe add some expletives without really adding them? Just a guess on this one.
It adds a little bit of dimension to the film that is understandable from context. This is anecdotal, by the way; I do not know any filmmakers.
And also, ^+1 to @VedranŠego comment to @Ankit Sharma's answer.
(It's also fun for people who do know the language - and can tell the direct translation is a little off!)