20 years ago you could block book advertising across three TV channels, a few newspapers, and radio stations, and be pretty sure you would catch almost everybody.
No matter how much you spend, you simply cannot block book all the channels that now attract our attention. The last 20 years has created communication channels inconceivable a generation ago.
Like time, attention is a non renewable resource, there is only so much of it, and unlike 20 years ago, there are almost infinite opportunities for us to spend our attention.
Marketers therefore have to reverse the order in which they approach gaining your valuable attention, as no longer can they easily access mass attention by intrruption. Now they have to earn the right to communicate, person by person, as just turning up and interrupting you will not work. Even if we happen to be there to be interrupted, we will ignore you without a very good reason to give you some of our valuable attention.