Hmmm well Prom you know I've worked in media sales for nearly 17 years (mostly press so I'm well aware of full page and DPS ads) and I have to argue against what you're saying.
Advertising IS measurable in some respects, the most effective is online advertising as it's a completely measurable source (page views, compressions, sales, referrals...etc).
6 or 7 years ago, Marketing execs would get a budget and just throw it to the wind, not really caring where or how, just getting the brand name out there in the best platform available (the good old days of making easy wedge
). However, since 2007 when whispers of recession caught on, budgets were revised and everything became about R.O.I. (return on investment). It's all about brand awareness, no companies cannot measure successfully the result on tv advertising, but it IS measurable by hikes in footfall to the stores or spikes in visits to the site (especially if visitors are immediately heading for or enquiring about something that has been advertised).
The way companies and ad agencies see it, they need to keep an awareness going, either to promote a new product or keep up a presence.I've worked with some of the major ones in the past (L'oreal, Max Factor, Waitrose, Mothercare, Peugeot...etc) - they are companies who will frequently offer special deals or new products so there is an arguable need for a presence within media platforms to promote the product and drive sales..
Another client I worked with, Unilever (who own half the world it seems) - do not bring out new products on such a regular basis, but will still keep their products advertised as it's a way of keeping it in the mind of the consumer. Advertising is a very seductive industry, no doubt about it. TV and radio ads are scheduled to appeal to a certain demographic, same with press. There's loads of research that's gone into why one product can appeal to a consumer more than another product that does exactly the same thing, and the main result has been promotion and brand attractiveness, not price.