Why is sampling essential for publicly accessible MCP servers?

Sampling is essential for public MCP servers because without it, the server operator would pay for every language model call made by every user. If your research tool fetches Wikipedia articles and then needs to summarize them with Claude, each user request would cost you API tokens. With sampling, each client pays for their own AI usage while still benefiting from your server's tools and data processing. This makes it economically viable to build and share MCP servers publicly without worrying about runaway AI generation costs from unknown users.