Depends on the industry but lots of advertisers just throw money out the window....still. Here's a million bucks to go spend on search...um, but your website has nothing for people to do on it and doesn't have any info related to the keywords and reasons you want to bring people to the site! It might be nice to play with those big budgets but at the end of the day it's just boring and frustrating to deal with the people who want to see "results" but don't listen to anything you tell them.
Since they have a big brand behind them, some conferences like to bring the big spenders in to do a presentation and as the agency you have to put words in their mouth and write it for them. :)