As discussed on Discord, the decision has been made to remove the system prompts by default, to better segregate the API and the UI usages.
A concurrent PR (#1353) is enabling the dynamic setting of a system prompt in the UI.
Therefore, if UI users want to use a custom system prompt, they can specify one directly in the UI.
If the API users want to use a custom prompt, they can pass it directly into their messages that they are passing to the API.
In the highlight of the two use case above, it becomes clear that default system_prompt does not need to exist.
a3ed14c58f