Please .... Get off the soapbox. Jealousy is one most primal and instinctive emotions. it's normal to feel in a small dose given certain circumstances, even if it's brief and you have to rationally frame it to calm it.
If you're completely devoid of it, it means you're not emotionally invested enough in that person. That doesn't mean be a controlling psycho but there are specific situations that can make any rational human being jealous. .