OpenAI CEO Sam Altman explained the company's shift from open to closed AI models in a Reddit AMA.OpenAI wants to hit the safety threshold for its AI models and believes closed models offer an easier way to achieve this.Altman acknowledged the importance of open-source models but emphasized the value of powerful and easy-to-use APIs and services.OpenAI has faced criticism for not open-sourcing its AI models, with cofounder Elon Musk being one of the vocal critics.