It does? I see constant complaints online from iPhone users asking how to, for instance, block ads on YouTube, only to be told "buy an Android and install Firefox" because ad-blockers on iOS don't seem to do this.
Are you talking about the browser or the YouTube app? Most iOS users watching YouTube use the YouTube app, not the Safari App, so they’re obviously asking how to block ads because the app isn’t a browser, not because Safari doesn’t allow ad blockers.
I'm talking about the browser. On Android, you can install Firefox + uBO and watch YouTube without ads. You can also install another handy extension so you can turn off the screen and the video won't pause, so you can listen to music on YouTube that way. You can't do this stuff in the official YT app.