Because they are a bunch of rich people who simply do not give a shit and the rules do not apply to them?
A snotty bully gets the lesson "there will eventually be somebody bigger" beaten into him. A snotty rich bully never actually encounters that.
That's what gets me, too. Though it can be easily copied, their service model is such a night-and-day improvement over the state of things previously that they should be universally loved for what they're doing.
And yet they keep pulling these asshat antics, and gratuitously making a bad name for themselves -- over and over and over again.
But more so, remember that everything's on a margin, here. Uber can obviously be very successful on the level of "a company that provides taxi services in a lot of cities." But they've taken in more than $10B in funding on the premise that they can be much more than "a company that provides taxi services in a lot of cities."
So even though it seems like they should be coasting into victory, they're actually super tense and worried, because what they could coast into victory for is not what they're now obligated to become, based on the money they've taken in and the promises they made to the people who bought them.