Apples and oranges.
Violent crimes with knives are not a problem. The only reason a person wants to use a knife to kill you is because they don't have a gun in hand. How many people can a single person kill with a knife in one event? In many cases requires a physical confrontation. Criminals don't want that.
Building a bomb takes time and knowledge, you got to read about it, you have to test it and so on. I would imagine stupid violent people don't like to read so that weeds many of them out.
It doesn't take much to blast a bunch of rounds in a crowd.
But hey call it what you want.