The reason I give to non gun people why I carry a Glock 19 with a loaded capacity of 16 rounds, is simple. I carry Insurance on our Jeep, not to get into an accident, but just in case, the Pistol carry is the same.
If never needed, it ain't so heavy, does not hurt, in fact I do not even feel it.
Many weapon deployment in the word of self defense, requires more than 5 rounds, and for that reason you will not find a Chief Special in my pocket.
The spare 17 round magazine, that's just for balance.