>Why would they? The entire point of YouTube Premium is removing ads.

You could've easily made this argument about Hulu right before it did the exact same thing being described here.

>If they put back ads, I believe that most people will simply cancel their subscription and get a renewed interest in ad-blockers.

Doing this successfully on your smart TV is a barrier that most non-techy folk aren't going to climb over. In the case of Hulu, most people just... accepted it. Same with the Amazon Prime ads you mentioned.