> Racist

One reason why Uber has been great for the black community is that hailing a cab has traditionally been more difficult. Studies show that Black patrons get lower levels of service and black waiters get lower tips than their white peers (because of enduring stereotypes).

> Sexist

Women are often tipped more based off of looks than their male peers. Similarly, warding off advances and harassment is a thing.

> Classist

A diner and a 5 star restaurant often have competing levels of service, yet % based tipping means that the restaurant servers take home much less more money. Similarly, things like crooked teeth can affect how your patrons regard your smile.

> consumers of both races discriminate against black service providers by tipping them less than white service providers