Honestly, because it is crazy easy to read sinograms. I only lived in Japan for a few months and casually studied the language, but I wasn't with any other foreigners so I was 100% immersed in the language. At the end of the few months I reached the point where I could read Japanese faster than I can read English. It's as if reading a phonetic language still has to go through a process of symbol -> sound -> picture -> meaning in our brains, where a more ideographic language goes symbol -> meaning directly thus cutting out a lot of the processing time. Given that any given text is going to be read thousands of times more than it is written, the extra complexity in writing seems well worth the trade-off.
What resources did you use to get so good at reading kanji so fast? A few months to be able to read all but the simplest japanese is really incredible for someone that doesn't already know kanji.
I don't see the book on Amazon, but it was a pretty basic Kanji book that made a point of sorting them out by radicals so you could see how things were built, nothing too special.
I think the key was I bought tons of manga for children, the ones where all the kanji have the hiragana above them so you can get lots of vocabulary and kanji reenforcement from those.
I'm not the parent comment but I used an Anki deck from Nihongo Shark. It sorted the kanji by radicals. I did this for 2-3 months before burning out, but it made learning kanji much easier since I could see the radicals that they were composed of.
I did that as well. That deck is basically (with a few differences) an Anki version of Helsig's "Remembering the Kanji". I started with the book, and continued with the Nihongo Shark Anki deck later. The system works incredibly well for the first few hundred Kanji at least, after that it gets harder and harder to come up with the mnemonic devices the method is based on. But by that time it also starts to get easier to remember new kanji by traditional methods (in my experience at least).
Even with my still incomplete number of kanji it does help tremendously with reading. It's faster and takes much less effort than trying to read just Hiragana (which I learned to read many years ago - it's still hard to read text written only in Hiragana). And with just kana you'll run into the homonym problem all the time too, unlike with kanji, and that doesn't make it easier either. Oh, and knowing the kanji can also sort out the (probable) meaning of a sentence even if I have not learned the actual word yet..
