Pistols - These are not considered a significant military weapon. They are easily concealed which make them threatening. The military helmets and body armor of today defeat the bullets from handguns quite well. One would need to go into illegally hand loading very light, and fast bullets to penetrate body armor. Modern armies on the other hand do have available armor piercing ammo to defeat body armor with their handguns. Handguns can be used to ambush or bushwhack soldiers as was done in France and the Philippines with these throw away guns.
Handguns have limited practical ranges. Most people cannot use them effectively over 21 feet. If you try to engage a target at longer distances the time required to acquire a good front sight picture and squeeze off a round increases. Some people can train themselves to shoot a handgun effectively out to 50 feet. I know you can shoot out Telephone Number List further but if you get into variables like the target is moving, bad light, taking cover, the target is hooting back etc you realize quickly these are short range weapons. I do understand that there are hunting handguns that can be used to shoot out at long distances even 200 yards but these are also bulky heavy weapons hard to conceal.
This makes every pedestrian within 20 feet of a soldier a serious threat. The soldiers have to stay alert and watch their back all the time. Hard to do with long hours and troops stretched thin. Drop your guard and thump you are dead. Now come vehicle stops. If the population is armed you have big problems with checkpoints. Two soldiers cannot work a checkpoint. Numerous personnel need to be deployed. Some need to be behind barriers so as to make an ambush seem futile. It is very easy to shoot a policeman or soldier in their unprotected face when they come to the driver window to ask for papers. Just ask any highway patrolman how nervous they get when they walk up on a car at night full of people when they cannot see their hands.