Out of about 2.7 billion users. So about 5% of all users are subscribed to YouTube.
If the same were true then Open AI at 1 billion weekly users they should have about 50 million subscribers. Right now that numbers sits at 20 million though and growth is slowing down. [1]
So people are more willing to pay for YouTube than ChatGPT and that is ignoring that YouTube is still largely relying on ad revenue and can only allow itself to have more and more ads as there are no alternatives. Open AI has plenty of competitors that would love to offer users free access if ChatGPT were to start showing you ads.
[1] https://fortune.com/2025/10/14/openai-subscriptions-flatline...