Not necessarily the case. It has been my experience that the presence of cars, parked and driving, make the pedestrian feel more secure, atleast on streets, and thus more likely to walk there. Especially the on street parking, ie the presence of a ton of metal between you, the pedestrian, and the street makes people feel very safe.
An example would be our our city's most pedestrian dominated district, one whose streets are packed & lined with cars (to the point where one can oft walk across the street at any point, the traffic is so slow).
Another example is a certain street in Cambridge, Massachussets, (cannot remember the name...) where at one time the city placed large planters to entirely cutoff cars and make it pedestrian only. Without the cars, the urban, normally pedestrian dominated area suffered severely, to the point where shops were going out of business, forcing them to reopen the street.
A final, obvious one is New York, perhaps the least car dependent area in the nation and yet, all the same, one of the most car trafficked.