The Chat-GPT models are all pre-prompted and pre-aligned. If you work with davinci-003, it will never say things like, "I am an OpenAI bot and am unable to work with your unethical request"
When using davinci the onus is on you to construct prompts (memories) which is fun and powerful.
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97% of API usage might be because of ChatGPT's general appeal to the world. But I think they will be losing a part of the hacker/builder ethos if they drop things like davinci-003, which might suck for them in the long run. Consumers over developers.