It's not the most "permissive gun laws in the world". In Norway you can buy a suppressor off the shelf with little to no paperwork.
If you live in CA and don't want to experience permanent hearing damage from shooting, you'll catch a Felony for simply possessing one. It's a big middle finger like the rest of California's gun laws.
I mean on Amazon you can buy them too, you just might have to look for something like a "lawnmower muffler for 9mm exhausts".
I'm pretty much a gun control maximalist, but I would be more than happy to barter suppressor restrictions for pretty much anything else, since I agree with you that there's a good non-shooting-other-people reason to want to have them and I doubt they're actually that relevant to murder stats.