A random thought while drying my hair –
Whether your hair (bangs) goes left or right is probably determined by which hand you use to hold the hairdryer in the first place / mostly of the time.
Actually, for me at least, I never change that choice of hand.
The more I use one hand, the easier to use that hand again. I feel awkward to use the other hand.
Thus that (always using the same hand) will pretty much determine how my hair parts.