I'm not sure if anyone else picks up on the increasing disharmony between the vocals and the video on the TV these days.  Seems to be more prevalent (but not exclusively) in cheap cheesy ads, and is most annoying. I guess these days it's churn out fast crap to get fast cash.
So I thought I'd start with an exercise on how it was done properly.  This is going back to the 1970s, so not a new phenomena.  The protagonists in this example are a domestic servant (miming) and a handyman (singing), and they seem to do a very good job of lip syncing. Of course there may be other views and thoughts and comment and examples good and bad are most welcome.

https://www.youtube.com/watch?v=GKhPVHoodrU