A possible answer is because the creators that have their own sponsors in their videos want the view even if you don’t see the Google ads, so Google on one hand want you to watch their ads while on the other hand cannot afford to really lose you since that would reflects on the creators and then if a creator leave for another platform (a big if, I agree) Google lose all the traffic generated by said creator, both who use an adblocker and who don’t use an adblocker.