'Those people' are still incredibly valuable for YouTube.
They watch content, and interact with creators which increases the health of the community and draws in more viewers - some of whom will watch ads.
They choose to spend their time on YouTube, increasing the chances they share videos, talk about videos, and otherwise increase the cultural mindshare of the platform.
Lastly, by removing themselves from the advertising pool, they boost the engagement rates on the ads themselves. This allows YouTube to charge more to serve ads.
Forcing everyone who currently uses an adblocker to watch ads wouldn't actually help YouTube make more money, it would just piss off advertisers as they would be paying to showore ads to an unengaged audience that wouldn't interact with those ads.