Some scouts don't need a gun, but use stopwatches, getting pop times or times from home to first depending on who they are scouting. I have seen scouts down the right field line pull out their phone and video a pitcher. Maybe they have the velocity info they want and are there for a 2nd, 3rd, 10th look.
However, there is nothing like being at a high school or college game and watch 8-15-20 guns go up!