Some people bruise more easily
than others but I have the opposite phenomenon: seemingly bruiseworthy events leave not a trace. I've been hit by cars, fallen off cliffs and crashed bicycles at speed. I might be very sore for days or weeks afterwards, but I don't get the blue/black/purple/yellow bruising that most people seem to experience to varying extents.
I write this now as I am layed up with a broken leg and have more time to ponder the mysteries of the body than usual.