I understand your complaint, but I don't really feel like it would be very feasible from a business perspective. Black cabs set their own prices. Uber trying to predict those prices is a lose-lose: anytime they underestimate the cost, users will be pissed they had to pay more than expected. Anytime they overestimate it, they risk the fact that some users who otherwise
would have called a cab may decide to figure out another option due to high prices. Uber just isn't in the business of predicting cab prices, any more than a normal cab you hail on the street is.
Yes, in an ideal world, they would estimate the cab price. But in an ideal world, iPods would come preinstalled with music and plane tickets could be purchased 5 mins before the flight at the same price. But these things just don't make business sense. I have a strong hunch that the time and effort put in by Uber to predict prices would only marginally increase their revenue, and certainly wouldn't increase their profits.