Americans also use tipping as a status signal, despite it being socially grotesque.
Even here on HN we'll regularly witness people proudly proclaiming that they've tipped 50% or more for "good" service. Not content with showing off their status to whoever had the poor fortune to be dining with them, and the waiter/waitress that served the group, they also relish in the opportunity of soaking randoms online in their lavishness post-factum.