Except Mandarin has a lot more homophones than English does, likely under the long influence of the writing system.

For spoken Mandarin, you can probably infer enough from the conversational context, but for official documents, business and technical terminology, or any literature, full romanization renders the text much less incomprehensible.

This isn't helped by the fact that Classical Chinese, from which most complex vocabulary is derived, is even more homophonic than daily speech.