Taxi's can't offer guaranteed service at certain locations and times precisely because they do not use the author's dreaded "surge/congestion pricing schemes."
When your professional society conference lets out at the same time that the local sportsball team's game gets over, and everyone is headed downtown to eat, the taxi company runs out of cabs because they're all cheap and everyone takes one. Uber surges the price to match the market demand, more drivers come out, and everyone who wants a ride can get one.
Under the pure cartel taxi system, if you need to get to the hospital because your wife called and she's gone into labor early, too bad! All the cabs are taken because they're so cheap and the demand is so high. Under Uber's system, the price rises to match the demand and you can pay for a ride.
It's no different than when people decry "price gauging" after a natural disaster. Go ahead and keep gas at pre-disaster prices, and 100% of it will sell out. Then, if you MUST have it, say to run your generator to power grandma's oxygen machine, too bad! It was all sold for $2/gal to a bunch of people who panicked and drank it all up even though they really didn't need it. If the gas stations had surged pricing to match demand, they'd be more likely to have some left, and while it would be very expensive, at least it would be available for people who really needed it, instead of being consumed by people who merely panic-purchased because it was still cheap.
Uber's surge pricing system is a virtue of their business model, not a vice.