What military units wear kevlar vests?

At this point I forget if they still even use kevlar but I know they use ceramic plates but I have seen shows on the military channel wear snipers are on top of roofs wearing their ACU/MARPAT pants and shirts (not jackets like their under shirts) but no vests is it because of the distance from targets because it still doesnt make sense since they are in Iraq and Afghanistan where anything could happen. I have also seen green berets without them (they were on a recon mission) but this mission took place on the first day of the ground war in desert storm so were they not issued at that time? Please leave details like when the vests were issued (also the helmets known as k-pots) and if there are any U.S. Military units that dont wear them