Criminals are not military troops. While there are always statistical outliers, criminals are about getting what they're after with the least possible bother -- otherwise they'd be honest people living honest lives working for a paycheck rather than robbing houses.
Criminals don't have the mission orientation and the training that military combat troops get to press on towards a goal after taking casualties.
Exceptions could happen but, given all the proof that most self-defense incidents are resolved by the mere presentation of a gun without the need to fire it even once, the probability of encountering multiple attackers dead-set on pursuing their mission after I've taken down one or more of their companions is low enough for me to be comfortable with a gun that is small enough to be concealed without having to wear a hoop skirt or a burka to cover it up.
Every activity in life involves balancing probabilities and risks. People need to do their own analysis and take into account their own, individual circumstances. Some people's physical capabilities and life circumstances make carrying a full-size, high-capacity, double-stack semi-auto easy enough that they can routinely cover that low-probability of meeting multiple, highly-determined, mission-oriented attackers who won't retreat after taking casualties. Other people's physical capabilities and life circumstances don't.