Reply #5: Because the only people who it would help are the people who are least able to advocate for it.

[Occam Bandage]

That is to say, it would really only help ESL learners. Meanwhile, it would have the following disadvantages:

1. It would require every living English-speaker to re-learn to read and write all over again, leading to slower reading/writing speed among all currently-literate generations.

2. The conversion would be enormously complex and difficult.

3. It would lose quite a bit of the encoded etymological clues. For instance, "phonetic" and "phonics" would no longer appear to be cognate.

4. It would have to decide to represent only one certain dialect, or else run the risk of having mutual unintelligibility. Most likely, different countries would take different standards, requiring a literate English-speaker to keep several dictionaries in their minds.

5. The whole shebang would have to be repeated every generation anyway.