McKinsey is a management consulting company https://www.mckinsey.com/ which is famous (or infamous) for promoting highly 'streamlined' business practices. They're known for turning around failing businesses into profitable ones but also for the enron and 2008 scandals with the housing bubble. Though I'm not too familiar with exactly what 'McKinsey' would imply, it seems to just be a shorthand for whenever a business starts charging for something that was previously free. Aka luggage fees.