In Spanish, they call strawberries, "fresca," which is the same word as "fresh." Fresh strawberries = fresca fresca. Some Spanish speakers, I would assume, think that the word for "fresh" came from the word for strawberries and may assume it is like that in other languages, like how we all use orange and orange. Does "salty" even come from "salt?" I think the better question would be, how come we use the same word for both of these?
But it doesn't come out of sugar cane by itself; it takes human effort, and a technology that had to be invented, to extract it. Not to mention that sugar cane doesn't grow in most parts of the world. And before people had sugar on their tables, they didn't know that there was such a substance in nature and had no use for a word for it. Which is why the English word sugar is ultimately from Sanskrit.
No we don't. However, it kinda happens witht the word for sweet and sugar (dulce y azúcar). They're different, but they have a direct correlation. However you can grasp it by the fact that a sweet (un dulce) is sweet flavored because it has sugar in it. I guess it happens with most to all of the languages?
That's just how Asian languages evolved. A lot of other languages use different words for the mineral vs the flavor/sensation. In Korean, it's doubly apparent because 소금 is Korean and 짠 is Sino-Korean. You also have to consider that these translations are not perfect or absolute. For instance, salty could also be 소금기 있는 in certain contexts ("there is salt essense" or "there is saltiness"). On the English side, salt could also be a verb or adjective and could even refer to a different mineral altogether as there are different kinds of salts (i.e. the 9 different kinds used in fireworks.)