international marketing

Why a unified global marketing campaign? I understand that there is only limited time for executives to review and approve materials but, given the importance of marketing, it seems wasteful in many cases to require a unified global campaign. I wonder if the desire is driven by the relatively uncommon travel profiles of senior executives - most customers will never see a campaign outside their home country - but senior executives are much more likely to see global brands in a variety of locations - and may be confusing their own rarefied experiences (and occasional jarring experiences where brands are positioned differently) with the everyday.