This is a good point but if new players really wanted to go on mass killing spree instead of going to the explosives npc they would just go to the hundreds of stores near the bank, purchase a gun and then just open fire. If anything the explosives npc should be moved to a different point of the map where it's less populated.
Another thing is that grenades are a good way of raiding if you want to clear out a base without having to pull out your special weapon and then wait for the holser. I rather loose a gradenade and a gun than a special weapon and I'm sure other people will feel the same.