I imagine OpenAI has no problem this, there are no secrets in the prompt, and it may be useful for prompt engineering. If it's harmless, no point in stopping the user from seeing it.
1. It could help competitors improve their alternatives
2. It could be used against them in a lawsuit, so they would probably want to keep it hidden until force to reveal it (which they would likely fight against)
3. It gives more information to the people crafting "jailbreaks"
4. It might create a backlash, considering how heavy-handed the "please make images diverse" part of it is
5. It might create ANOTHER backlash, on the other side of that coin, for not being heavy-handed enough, and not explicitly listing an ethnicity, gender, or whatever other personal characteristic that some might want ChatGPT to represent by default in its prompts