The military and LE don't "start people out" with anything but a standard issue duty weapon. Depending on the student, DA triggers on handguns like revolvers or autos like a M9 can be difficult to use for an extended perios, and managing that DA shot is a major "first hurdle" to work through. During this learning period, if the student doesn't rapidly improve, it may result in that student becoming more fatigued and discouraged, which may compound into a reduced level of confidence. Personally, I will allow a brand new handgun shooter to initially use a .22, just to get used to the "idea" of firing a handgun. Just some simple grouping at short range, and maybe 1 or 2 very basic drills. This is only for a 3-4 of magazines, and I will often have the shooter fire the 22 "orientation tables" with a suppressor attached for the first half, then without for the second half, then move on to the center fire handgun.