Air shows are for the most part trade events, where manufacturers are showing off their wares to business and government representatives. Everybody knows that an airliner's handling at maximum take-off weight, full of passengers, luggage and fuel, isn't going to be anywhere near as spirited, but the test pilot is going to put on a show to attract the interest of potential buyers.
It's the same for the stunts that some fighter jets are put through where they appear to defy the laws of physics - it looks good, but try bleeding energy off like that in a real dogfight, and you are quite likely to end up a sitting duck.