The surge pricing model sounds like a great incentive but it's also very easily exploited. Drivers that would otherwise have chosen to work full time might choose to only work during surges, ultimately reducing the total capacity of the system and increasing prices.

There are also reports of groups of drivers working together to manipulate the surge price in order to increase earnings[0].

[0] https://www.distractify.com/p/uber-surge-pricing-hack