If it provided the value everyone says it does, then charging the amount of what you would generate for ad revenue doesn't seem like a huge ask.
Vast majority of Youtube viewers do not pay for Premium. No one pays for Google search premium. No one pays for Instagram or Facebook or Whatsapp.There are certain class of services that work best with ads driven business model. ChatGPT is one of them.
If Google and all other search engines locked search behind a subscription, it'd do a great disservice to the world since it means the poor can't use it.
Except that this product isn't comparable whatsoever to Youtube. Contrary to your point, there are whole businesses popping up because people are paying for search engines due to users feeling that Google's results are insufficient for serious search. I'm not sure this is a proper comparison.