A marketing team is using a large language model to generate social media posts for a new eco-friendly water bottle. They are frustrated because the generated text is often too generic and lacks a clear call to action.

Example of their current prompt: "Write a social media post about our new water bottle."

Example of the model's output: "Check out our new water bottle. It's great for staying hydrated. You can buy it on our website."

Based on the information provided, analyze the primary weakness in the team's current prompt design and explain why it leads to the undesirable output.