Maybe it could. I believe the market of advertising on marginal websites is small, and it's not worth the trouble for Google to try to work on that market: the number of users of these websites is small, and the number of advertisers wanting to advertise on questionable websites is also small.
> I think it's naive to think that they are purely doing this to protect Advertisers' convenience.
It's not just convenience. When advertisers are unhappy, Google loses a lot of money, because ads make the most of Google revenue.
If you have reasons to believe otherwise, please explain.
* all these websites account for at most 1% of Google Ads network reach by the number of page views
* since these websites are to be opt-in, the advertisers' competition will be much lower, probably 1/10 of the usual click price
* since the number of advertisers will be low, and only marginal advertisers would opt-in the marginal website list, the relevance of ads (and thus the probability of a click) will be also much much lower, probably 1/10 of the usual click rate
So by banning all marginal websites Google loses only 0.01% of revenue from ads network. If my back of the envelope calculations is at least order of magnitude correct, this does look like a very little price to pay for relief from a headache associated with working with questionable websites.
I think it's naive to think that they are purely doing this to protect Advertisers' convenience.