I understand and respect the value of redundancy. I just don't find that prepositions provide very much of it. They serve as placeholders to help us parse a sentence. But the difference in meaning between them is so slight in most cases, and zero in many others, that the choice of one preposition over another rarely helps us solidify the meaning of that sentence if there's any ambiguity. As an IT professional I work with Indians every day, and the selection of prepositions in informal speech in Indian English is often almost haphazard. Yet it's extremely unusual for that to cause a misunderstanding--even in what to us Americans is a heavily accented dialect in which a little redundancy might actually be useful. I have often said, only half in jest, that the primary function of prepositions in English is to identify native speakers. You haven't convinced me of that. My continuous experience of understanding Indian English reinforces my conviction that in the overwhelming majority of cases prepositions carry no denotative meaning and are only grammatical markers. Distinctions such as that between "in the box" and "on the box" or "to the village" and "from the village" certainly arise, but not very often. Coincidentally, that's a classic example I often use to make my point. Please explain how you would describe that extremely subtle difference to a foreign student. And once you've done that, please craft a situation in which that extremely subtle difference is important. I seldom hear people say the entire phrase "unleaded gasoline." They usually just say "unleaded." Sometime in the 1980s, when cars requiring leaded gas were no longer manufactured in the Western countries and each year a greater portion of the population bought only unleaded gas, the phrase "unleaded gas" was shortened to "unleaded." It has replaced the noun "gasoline" in vernacular speech. The term has spread into other applications. I work in Washington DC, whose ancient water system has become legendary. There's a special faucet delivering near-boiling water for coffee or tea in the lunchroom, but I always bring in a cup of cold water from my Pur filter pitcher and heat it up in the microwave oven. People ask me why I don't take advantage of the convenience of the tap, and I answer, "I prefer unleaded."