Well.. habit but once i realise whats happening I usually stop..
Also.. on a forklift, the transmission stick is on the left side of the steering wheel.. usually where the blinker or wipers are depending on your car.. when you get used to flicking that switch for 10 to 12 hours, you find yourself in real life flicking it to go forward. Im sure ive confused some people at dead stops by signalling right and going straight..