Dear Eva, this is a very interesting question and shows the importance of English politeness. I dont' think that all languages use politeness in the same way. In my native language (Italian), for example, we may say "pass me the salt" with a slight question-like intonation at the end ("mi passi il sale?"). We may want to add "please" ("per favore") at the end, or not. I know this would sound rather rude to an English speaker, but that would not necessarily be the case in my language.

I speak Japanese - you generally cannot use the equivalent of "can you" (i.e., to be able to) to make an indirect speech act of requesting in Japanese. There are of course ways to politely request things and there are of course ways to make indirect speech acts in Japanese, but for a request, this particular structure isn't generally used.

Most langauges have indirect speech acts and many use them for politeness, but I don't know how common that very specific combination is (i.e., ability = request)