once as the car industry, I think the reason for this situation is now drops to send a single logical problems, lead to the guide and driver intentionally increase orders slow.
you may notice that this interface, when a taxi, the fare options on the default interface (and also increase a lot!), the user can choose to add different prices, but the platform will tell you the possibility of orders with different price, if one is not single, you can adjust the price called the car again.
platform planing to profit pressures, such rules will bring what incentive to both sides of the platform? The driver know users can repeatedly choose increases, so the driver to select the first answer does not increase the burden, he knew you couldn’t get to the car will improve the Italy with tips. So the result of this rule is that passengers repeatedly to increase the price to call the car, a waste of time, it is likely to pay more expensive money. Under this rule, the two sides will play "fancy game", but the result is both a waste of time (which is the most important parameter to maximize the efficiency of the taxi system), users spend more money, give the rules more profit space.