Each year $1,000 is spent on every single American (adult, kids, grandma) in the States. I often say and also experienced from my past experience in a Marketing department, that while we all agree to say " I don't really know how effective is the ad but we better be in the mag as all our competitors are". Good chance that your competitors are thinking the same way you do.
That is the reason why so much money is spent on Interruption Marketing. To be effective, companies thing they need to in as many mag as the competitors. and if they do more coverage, they think they have a better grab on their potential audience.
But the conclusion is that the more we interrupt, the less people pay attention. The first reaction companies do, ads don't work as well so we need to place more ads to become effective and here goes the vicious circle.