In countries with strong central banks, the economy is mostly inflating and deflating itself. The central bank attempts to guide it towards a target. The observation that central banks find a low level inflation valuable stems from the fact that the target isn't zero.

One reason the target isn't zero is price stickiness. For instance: people react irrationally to drops in their wages, but, obviously, the price of an hour of labor can't be steady: it moves up and down just like anything else that can be bought or sold.