It is one-way to encourage flow of traffic. You can't see cars approaching the exit, so when a car illegally turns in the exit, there is a huge potential for a head-on collision. I've had this happen to me several times. I agree the whole layout of the station parking lot is inconvenient, but it's a small space and keeping traffic flowing one way in and one way out seems to be safest.

On my most recent trip, I saw this happen again. Yes, "the current arrangement is an inconvenience" but so is a head on crash....