Why is Revanced Able to Exist?

Genuine question I've thought about, especially with the recent attempted crack down by Google: why is it that we have been able to have apps like Vanced and Revanced for so many years for YouTube?

If Google is so dead set on blocking it, why don't they switch to an ad/app model like Netflix/Hulu/Facebook/etc use which can't (or haven't) been exploited/blocked (that I am aware of)?

What makes the YouTube and YouTube Music apps different to where they can be exploited and patched to enable Premium features and block ads?