Just> Everyone would be obligated to become a doctor in order to save lives. Rav?Moshe Feinstein zt”l famously rules that no such obligation exists.
Self-protection from attackers is different from being a doctor, and obligation would be different. And even when one is not obligated, we have a lot of people who are trying to be super-frum in mitzvos. Maseches Taanis describes a doctor who was visited by yeshiva shel maaleh more often than Abaye and Rava (despite his bloodletting methods were not the most effective ones – surely a fact known b’shmayim!). I would presume many would like to follow in his steps.