oh wait, they don't - because they are illegal and highly regulated.
OR, it could be because they're expensive, ineffective, don't last, and hurt accuracy. Or because most murders are not planned out in advance, in excruciating detail, by criminal masterminds (or even the crooks in episodes of Columbo). Somebody who finds out their spouse is cheating on them and decides to kill them in a fit of rage isn't going to care about a silencer.
Likewise, gang on gang crime over drug deals doesn't seem to involve a lot of stealthy, hit-man style assassination stuff. Those guys don't need silencers.
And the people who do want one and want to avoid your regulations? Well, they just build their own, no license, background check, or anything else needed.
It should also be noted that in some European countries, suppressors are required when shooting in a close enough proximity to a neighbor that the loudness could be an inconvenience.
Suppressors are dead easy to make out of household products as is, they just aren't worth more than 2 shots. Likewise, any individual sent as the imaginary "hitman" that everyone seems to believe exists, would probably be aligned with a group with enough finances to either buy legitimate suppressors, or procure them from the black market.
The only people that cannot purchase automatic weapons and restricted modifications (suppressors, grenade launchers, etc) are the poor. The legal roadblocks are overcome (perfectly legally) with money.
That isn't the kind of gun violence these emotional responses are trying to stop, though. Situations like Boston and Connecticut are planned incidents. They don't use silencers for the reasons you list because they aren't trying to conceal their crimes, they just want to kill as many people as possible, and silencers hurt accuracy.
People just ignore the slaughter of spouses and mass murder of the destitute on the streets in favor of only focusing on shooting sprees.
The emotional rage murder would be culled by stricter gun laws, but gangs and mass shooters will just go to underground channels to get their armaments if they can't try to get them legally.
It's also important to understand that suppressors are not silencers. Most movies depict a suppressed handgun as sounding like an air rifle: that's just not the case unless you're talking about specially built firearms (integral suppressors, no leaks for gas) with sub-sonic rounds. I am going to guess that very few crimes have the monetary pay-off to justify such an investment (and if they do, the criminals can certainly afford to purchase a CNC machine and manufacture a supresor themselves).
On the other hand, a regular 9mm handgun or a .223/.308 rifle with a suppressor will still be very loud: comparable to a car's engine back firing, a tire blow out, or a firecracker. That's definitely a reduction in noise compared to a regular gun shot, but while one such noise might go unnoticed, a rapid succession of such noises certainly will.
Often these trivial laws are passed in order to be catch alls. You might get off on a technicality of a murder charge, but they get you for the illegal silencer.
Remember, they got Al Capone on income tax violations.
Please don't interject facts into this discussion! This is Hacker News, where we should just say what we THINK might be correct, or should be correct, without having any actual knowledge of the subject. That's what real hackers do, right?
BTW it's worth pointing out that some countries like Finland do not regulate silencers/sound suppressors on the grounds that they reduce noise pollution and benefit public health by reducing the risk of hearing damage:
http://en.wikipedia.org/wiki/Gun_politics_in_Finland#Related...
The post I was replying to is largely correct. Criminals don't have suppressors because there is no secondary market for suppressors due to regulation. That said, I would guess they wouldn't need or use them even if they were available.
I mean look at all the silencers people have to get away with murder - oh wait, they don't - because they are illegal and highly regulated.