[radley]

That's not correct. A few years ago YouTube changed their TOS, so they're now allowed to show ads on any content, regardless of settings.

[amadvance]

You're mixing up two different things. It's true that YouTube now places ads to small channels that have not reached the monetization requirements.

But after the channel satisfy such requirements, like 1000 subscribers, the creator gets control of the monetization and they can choose.

For any major channel you watch, it's the creator decision that you see ads or not.