Last time I had to parallel park was a couple of years ago (I don’t have a vehicle here). Without a doubt, every single time I used my turn signal to indicate I was going to park in a parallel parking spot and I drove, as one’s supposed to, to be next to the vehicle in front of my intended parking spot, either (1) someone would drive into the spot or (2) someone would drive up immediately behind me blocking me from backing into the spot. Usually it was number 2 and the moron behind me would get incredibly irate that I had shifted into reverse.
Driver’s education is wasted on some folks.