Phonemics is more important than phonetics for these things. Sometimes two sounds need to be represented with the same letter if they are similar and their difference is context-dependent.
Then there's also the etymology and handling of grammatical endings. Polish spelling would be more difficult without "rz" for example, despite its two sounds already existing elsewhere in the spelling system.
Then there's also the etymology and handling of grammatical endings. Polish spelling would be more difficult without "rz" for example, despite its two sounds already existing elsewhere in the spelling system.