A lot of advertising is not meant to increase discretionary spending, but to make you pick product A over product B when the moment comes to choose over alterna

A lot of advertising is not meant to increase discretionary spending, but to make you pick product A over product B when the moment comes to choose over alternatives. At the very basic level of it, advertising is giving out the information that your product exists, because otherwise, nobody would even know its existence. Your example for Apple is very good, it's very highly probable that some persons only switch to newer iPhones when they hear the news it exists and see the keynotes/articles about it, even though there is nothing wrong with their phone, and they may not be thinking about changing it.