I'm pretty opposed to tipping as a practice, or at least the reduced minimum wage for tipped positions, but I was expecting more from those articles. If you strip away the appeals to identity politics they are much less interesting or compelling. The WP article basically goes away save for a handful of cherrypicked sources. The Time article retains some vague handwaving about how many restaurant workers were former slaves around the time tipping caught on--how do they fail to draw a clear connection to racism in a time when overt racism was a point of pride?