I park in a standard parking garage, with forward angle parking and one way traffic flow. I occasionally encounter vehicles reverse parked, which confuses me, but whatever, but then also encounter vehicles driving backwards (well, forward facing, going against the posted signage) through the parking garage. This is always a big headache, because again, this is a one way parking garage, and for some reason THEY never seem to think they should back up or get out of the way of the person driving the correct way through the garage, so I always have to do some extra maneuvering and wait for them to pass, and I usually only have a small margin before the train arrives, and--
Assuming they are not simply idiots who can't follow the signs, my next assumption would be that these are the people who are reverse-parking, looking for a spot to back into.
Anyway, if you have difficulty making the turning radius to pull straight into a forward angle parking spot, there is a very simple trick: make a three point turn, attempting to pull into the spot to the right of the empty spot, then when you are almost to the bumper of the parked car, back up and straighten out, which puts you at the perfect angle to drive straight into the angled spot now in front of you.
It beats the pants out of getting halfway into the spot before realizing you're about to hit the car on one side or the other and trying to straighten out after the fact.