"I walk on a small bridge."
This is one of the examples of tonal variants in Japanese. 同音異義語 (どうおにぎご), or homonyms, can be defined by their accent for the ease of the listener. Above is the perfect example, where we have 椅 (bridge) being 'confused' for 箸 (chopsticks). Yes, it is obvious which one it is. However, it can also be noted thus: 椅 emphasises the first syllable, "HAshi", whereas 箸 is said like, "haSHI". Another example would be 川 (river), which can be pronounced "KAwa", and 皮 (skin), pronounced "kaWA". Hope this makes sense!
No, that's not the main reason. It's because English allows all kinds of sound combinations, as well as consonants at the ends of words, so we have far fewer homophones. Japanese, with far fewer allowable sound combinations, is loaded with them, but kanji helps us to know which meaning is meant when you are reading, which provides less context than speaking does.