Some random stats I found estimate that advertising is currently a $500B yearly industry, which means Google is only 15% of the industry.
Also, print ads, given a sufficient niche-ness of the magazine, are way better targeted to actual customers than web ads.
[1] http://www.bloomberg.com/news/articles/2014-03-03/advertisin...
If that were to be split 3 ways between Google, Facebook, and Everyone Else, Google might get $167 billion in revenue, or (at 20x PE) $3.3 trillion market cap.
I didn't say they don't have an impact, I said it's obscenely difficult to gauge attribution and online ads weren't the panacea they were supposed to be because it turns out people don't click ads. Despite this, advertisers are still advertising. An increase in ad spending is not any indicator that ads are working well because no one has ever known how well they worked.
To be fair to offline, you can get a pretty good read on store sales as a function of advertising if you do geographical splits. Its modelled, and statistical, but there's definitely nothing wrong with that.
I think the online problem is harder because its so easy to measure clicks that people focus entirely on them without considering other approaches, whereas with offline its hard to get any measure, so people are willing to try different things.