OpenAI has half a billion active users.

You don't need every individual request to be profitable, just the aggregate. If you're doing a Google search for, like, the std::vector API reference you won't see ads. And that's probably true for something like 90% of the searches. Those searches have no commercial value, and serving results is just a cost of doing business.

By serving those unmonetizable queries the search engine is making a bet that when you need to buy a new washing machine, need a personal injury lawyer, or are researching that holiday trip to Istanbul, you'll also do those highly commercial and monetizable searches with the same search engine.

Chatbots should have exactly the same dynamics as search engines.