Why did amir and baba fly kites?

The Soviets have invaded, and they do not like those who are rich and stand above others. Their Communist regime is geared towards making everybody the same, more or less. As Baba and Amir are highly privileged (they have the prettiest house in Kabul, I think it is said, and of course Baba has fancy cars and such American-like things) they are a target. Amir and Baba need to escape, before something bad happens to them.