How come?

Hair generally seems to grow downwards (unless very short or unruly) - head hair being the main example except for cow licked or particularly thickly stranded, leg hair, arm hair, eyebrows (apart from the wild unruly variety sported by occasional older gentlemen), even the unmentionable pubes. So standing squashed between two tall hairy men on the tube this afternoon  I was surprised to realise that chest hair (based on my unscientific survey of two white middle-aged males) grows upwards. Why is this? And how come I've only just noticed this now? I'm normally quite observant!