Baffles me why anyone is excited about this. Admittedly, I can’t remember the last time I even used FaceTime.
I think you might have answered your own question. But, for me this is why it's "exciting"(I'd probably use the word convenient, but hey).
I got three distinct communication needs. professional, social and family. Social could proably even be split up into technical, and "normies". Professional, and technical social, doesn't benefit one bit from this.
But, the family, and normies-social certainly does. Very often, when my other half is on the phone with one of our family friends, arranging god know what weekend activity, she will drag me into the call to hear my opinion on things, this often happens by just her putting the phone on speaker.
Similarly, when on call with family, one of us, drags the other person into the call. Or, the other person just invites themself into the call because they want to say hi to whomever is on the other end of the call.
Facetime video calls are a pretty common way for us to communicate with family, and normies, Being able to just hand off the call to the TV and pop the phone in a stand infront of it, having a poor mans teleconferencing setup by the click of one button, is nifty.
Also, finally, there is a family use case, being an international couple, where on xmases, birthdays etc. We dial in family members that cant make it in person, to say hi. Again, being able to connect them to one of the AppleTVs (in the kitchen/dining room or livingroom), would be an upgrade on the always slightly award that assures when one of the elderly relatives abroad wants to say hi to everybody.
Is it life changing? No. Is it super innovative? No. Is it a nice feature to have? Yes.