There are as many laws as there are jurisdictions, so "are there laws somewhere" is usually yes, regardless of how silly the law may sound. (It's still the law, in most of the US, that someone has to precede a motor vehicle - on foot - with a lamp, to let everyone know that a motor vehicle is coming [so you can start calming your horse to make sure it doesn't panic]. It's not enforced, but is there such a law? There sure is.) There are probably still laws that require you to unstring your crossbow before entering certain places.
Once a law gets put on the books, it usually stays there, because by the time it becomes too silly to enforce, no one wants to bother to sue to have it removed.
So there very well be laws somewhere that cameras that are in cellphones have to make a "camera-like" noise when taking a picture. And if one place a manufacturer sells its phones has such a law, it's simpler to just put that feature into all phones, than to maintain one stock for that place and a different stock (exactly the same except for the sound) for everywhere else. (It's cheaper for the manufacturer too.)