It's not the advertisers doing that, it's the publishers.

The advertiser has no real say in how a publisher decides to pimp their audience other than lining up with cash on hand like an eternally and unhealthily addicted John.

In fact, on the advertiser side it's mostly a prisoner's dilemma driving their addiction, pushed to spend money on poorly converting and too wide channels out of fear that if they don't and their competitors do that they'll lose market share.

Advertisers suck for a variety of other reasons, but let's not turn a blind eye to the publisher greed either.