I disagree that it's unfair to expect apps to work without reading. Some apps, sure, but I think a taxi application ought to be usable without being able to read. Consider
1. The user is drunk, and can't understand meaning of the text.
2. The user is preoccupied with other tasks, and skips over the words.
3. The user is illiterate. Functional illiteracy is prevalent in the United States, and being unable to recognize the characters of one's own language continues in many countries, too
My company invests in ensuring many of their products are usable for the illiterate. I doubt it's the only company that does so.