Does that number matter?

What’s the conversion rate on any single typical ad hosted by Google? Yet it all adds up to make a lot of money, for Google and (presumably) the advertisers.

Indeed it matters. A popular website is only financially valuable if the site owner runs ads on it, as Google does. Without ads, ChatGPT's consumer business model is not much different from WinRAR with its soft 60-day trial period. Sure, some % of its users upgraded to the full thing. Everybody else had humbler use cases covered by the free functionality (the 60-day expiry was famously not enforced).

Once zip/unzip technology became commodified (either by being baked into the OS or open-sourced as happened with 7zip), paid 3rd party tools were no longer needed and WinRAR's business disappeared.