Sometimes Sunset Shimmer worries that her girlfriend only loves Sunset for her super muscular DEMON FORM, with bat wings and sharp claws and fangs and...is it hot in here? (Whew!)
Humans aren't nearly as robust as ponies. Simple gestures such as hugs, pats on the back, and hoof bumps are all well and fine when it's another pony on the receiving end. With a person a fraction of their mass, ponies forget how fragile others are