Just a thought but maybe it’s the fact of control? With a gun they can control every human life they suck the breath out of, watching the torture of the very thing they hate, rather than a mass one stop shop action. We are dealing with crazies here and control is a huge factor.
That's ridiculous. It's easier to kill people with guns. Think of the steps required to use a gun vs. build and plant an effective bomb.
Bomb:
1) Research bomb-making. Find a plan that works. Make sure you do it on a VPN so the FBI doesn't catch you.
2) Buy bomb parts. Determine means of detonation (remotely, locally triggered, etc). Make sure you don't buy all the bomb parts from the same area so the FBI doesn't catch you.
3) Build bomb.
4) Test bomb. Realize your bomb-making sucks because this is your first time to build a bomb.
5) Build another bomb. Maybe it works on the second try?
6) Plant the bomb. Hope you don't get caught planting the bomb. Hope someone doesn't find it before you detonate. Hope it doesn't detonate on its own when no one is around. Hope it goes off the way you think it will.
7) It doesn't. Start over.
I don't want to put words in @Dago 's mouth, but I think that what he's saying is that, even if guns are easier to use than pipe/pressure cooker bombs, in the absence of guns, if someone wanted to perpetrate a mass killing, pipe/pressure cooker bombs are not so hard to make that it'd deter someone from using them.
There honestly probably would be an uptick in other means. It's happened elsewhere. The salient point is that other means simply aren't as effective as using a gun. So while there may be an uptick in other means, net fewer people will die.