These aren't just estimates, they are minimum bills that are purported to be based on "time and distance of the route"[1] and if they systematically and intentionally padding time and distance that sounds an awful lot like fraud. IANAL and it may not be technical fraud but it is at best a deceptive business practice and again one of the reasons we have taxi regulators.
[1] https://help.uber.com/h/d2d43bbc-f4bb-4882-b8bb-4bd8acf03a9d