Actually I may have a theory on why this is so annoying. Most people in Western countries are used to not haggling, and hate dealing with haggling for the two B2C products that are frequently haggled for, cars and housing, and frequently come out of the transaction feeling ripped off. And now Uber is trying to apply a faceless unilateral "take it or leave it" haggling process.
Yeah sure, but Joel Spolsky does point in this article how it pisses consumers off. And I think this sort of algorithm "pure" price discrimination based on mind reading how much the consumer is willing to pay is much more annoying than doing it by having cheaper and more expensive options.