Boy, did I ever get exposure to homophones when I learned Chinese. Chinese has loads of homophones, and somehow they get by. Somewhere along the way, tones were invented to help out (or perhaps they were always an integral part of the language), but even then, there are words such as "hao" (good) have three different tones, yet mean the same thing. Depending upon the context, it can sound like a first, second, or third tone (there are only 4!).
As a result of homophones, Chinese has very few one-character words. The word "pengyou" means friend, yet if you were to break it down, "peng" and "you" can both mean friend. To avoid ambiguity, the two are stuck together to make the word more distinct. (admittedly, I think the words were also stuck together because of an innate sense of rhythm in Chinese, who like words/phrases to be 1, 2, 4, and 8 characters long).
I guess that was a bit of rambling -- I agree with you that people do leave terms more ambiguous on purpose, but again, they seem to do it because there's no need to be more granular. Some cultures/languages only have a small handful of color words, while others have a plethora. They often have a "grue" color, which is both green and blue, because in their daily lives, it's not as important to differentiate between the two. I'd bet, though, if they discovered that green berries were poisonous while blue ones weren't, they would quickly devise a new color term or some other language invention to describe the poisonous ones!