Last time I walked from a hotel near Grand Central toward the convention center I caught Halle Berry leaving one of the studios. There were a couple dozen people waiting, a decent portion of those were security enforcing a perimeter around the door. Even when the public knows exactly when and where a person is going to be, the boldness required to gain access to a reliable and fatal shot would be tough to do.
Outside the front door of a random hotel? One of hundreds on the island? With all sorts of people walking in and out constantly, getting dropped off and picked up? You don't just accidentally find a powerful CEO and take a random shot lol. Wild.