- Native Mandarin speakers don't need it.
- It's nothing but a crutch for English speakers who can't handle learning the characters directly.
- Once the language is mastered, pinyin is useless; therefore it's an artifical and unnecessary intermediate step.
But after some discussion with my coworkers, about 80% of whom are Taiwanese or Chinese, and reading some web material on the subject (including the excellent Wikipedia article referenced above), I discovered that these assumptions are dead wrong. Wrong, wrong, wrong, to the point where I'm embarrassed at the level of my misunderstanding. Here's why.
Far from being just a tool for Western students of Mandarin, pinyin is actually used in schools in China to teach Mandarin pronunciation to children. After all, it's not as if one can see an unfamiliar character and sound it out as one can with alphabetic languages. The reason I was not aware of this before was that my parents (and I, by extension) learned Mandarin the Taiwanese way, where the Bopomofo phonemic alphabet---which does not use Roman letters at all---is used to represent sounds. So Taiwanese speakers of Mandarin have no exposure to pinyin, and in my life I have associated far more with people from Taiwan than from China.
Furthermore, pinyin is far from useless even once a full vocabulary of Chinese characters is attained. The existence of a standard romanization system eliminates confusion resulting from multiple arbitrary ways of expressing the same sound; the common Chinese surnames Wang and Wong are actually the same, but that's not obvious without a consistent representation. Libraries that carry Chinese language materials use pinyin to alphabetize their books on the shelves. And pinyin is invaluable as a method of expressing Chinese words on a computer, ever more important as we head deeper into the digital age.
I am humbled by my misguided arrogance, and encouraged by the implications of my new knowledge.