[akavi]

Why do you have less context in writing than in speech?

I'd be willing to bet heavily that the vast majority of those "homophones" are primarily writing-only, domain specific or archaic "shorthands", which are referred to in speech with slightly more verbose alternatives. Switching to a non-character based system would admittedly in that case mean some domain specific writing would be slightly less compact, but that seems a reasonable tradeoff given the unwieldiness of the current writing system.

[fenomas]

> I'd be willing to bet heavily that ...

You'd lose your bet. In that "shuu" link as an example, most (10-12 or so) are common enough that you might hear them in a typical newscast, with that pronunciation.

What makes things manageable is the combinatorics. E.g. there are dozens of kanji read "shuu", and many dozens more read "kan", but most of them are only read that way when part of a 2-character compound, and only a small subset of the possible "shuukan"s are words, and only a subset of those words are common in spoken conversation.

Even then, it is a very homophone-heavy language. I can think of four "shuukan"s off the top of my head that you might hear from a newsreader; it would only be after those that you'd get into domain-specific words. This is pretty typical.

[fourneau]

It's not that you have less context, as much as you /need/ less context. Instead of a few extra words to describe something, you get a different character.

Here's a great example of how in writing you can disambiguate "aunt"/"older woman": https://twitter.com/MaggieSensei/status/765769637372030977

In the above example all three are read as おば (pronounced: oba). When spoken you still need to differentiate, but it'd either be obvious from context or you'd just explain it manually.

[cthalupa]

Because you are going to select different phrases and words while speaking than you are when writing. Even with context clues from the conversation, it can at times be confusing, so you have to explain what you meant. Usually it's verbal, sometimes it's 空書 (sky writing). To avoid having to do this frequently, people will often adopt a subset of the language that is less prone to confusing homophones for their vocal communication.

It creates a situation where you have people who have wildly different voices in their writing than they do in their everyday speaking, which is an interesting phenomenon. (To me, at least)