An ad which is relevant to 1% viewers still sells, likely enough to keep it published.
But it's irrelevant to 99% of the viewers, and it's impossible to tell them from the 1%: among other things, because the viewers are not keen to share too much data about themselves.
I think we should see ads as the (annoying) cost of commercially-produced free content. I wish a micropayment solution would take off to allow for easy and reliable paid opt-out on multiple sites I might visit. (I already have Youtube Red, and it's great.)
