"Why does the .357 SIG need to exist? In the military one uses what one is issued. There is no sitting around reading articles and picking out exactly what one wants. In most LE agencies, one carries and uses what is authorized for carry/use. There may be some latitude, but one will not be able to do as one pleases. One will have to abide by policy. Private citizens can choose to carry/use what they want to carry/use. The multiplicity of calibers available for rifles and handguns testifies to the tremendous variety of choices available. People make their decisions based on a lot of different factors, of which ballistics, etc., are a partial factor. Sometimes, people make their choice based on a particular type of handgun. Sometimes they even make those choices based on popular mythology... i.e., that a particular caliber is somehow superior that other very similar calibers.
"People should not be afraid of their governments. Governments should be afraid of their people."