Model providers need to see your prompts in order for their models to provide responses. However, before your prompts are sent to the model providers, DuckDuckGo removes any metadata that contains personal information (for example, your IP address), and sends the prompt via DuckDuckGo's servers. This means that prompts appear as though they are coming from DuckDuckGo rather than individual users.
This help page has more information on how we make Duck.ai private and anonymous.