Why does my monitor need to do that? My OS, the Intel Management Engine, my application, the website I'm using, my internet provider, my modem's hardware stack, and the several networked microphones in my home are already doing it.
Consider the case where there's a quiet observer looking at the screen alongside you. The monitor also needs to identify them so that it can ensure that you're not an accessory to thoughtcrime by letting them look at your screen.
Your comment is very similar to past comments in HN where the user was sadly not being sarcastic (generally people with defeatist attitudes). Please use the widely-accepted sarcasm symbol. Example:
I don't think that really caught on that much. Film studios care about it, but TV manufacturers don't really.
This is for advertising plain and simple (and probably selling user data to some extent). That's direct income for the manufacturers so they care about it a lot.