[Hamuko]

You should be expecting it if the car is indicating, which is something you should do when you're about to park.

[doublement]

If a person is walking north, about to walk past a parking space, and a car is heading south and signaling left, it's very surprising to see the car pass the person by, then suddenly reverse and try to enter the space. Once the car is past, most people assume it's signaling to turn farther along, instead of about to go backwards.

EDIT: To be clear, I'm describing a perpendicular-parking scenario, where people usually make a right angle turn going forward to occupy the space.