There are some missions where a suppressed weapon might be useful, like surreptitiously taking out a sentry. That’s why SOME special operations units will have personnel armed with H&K MP5SDs. Or suppressed 9mm or .22 cal pistols. With the appropriate sub-sonic ammunition. But a DOD sized issue of suppressed stuff? Not going to happen.
Silencers suck. I almost always have to get two head shots with a silenced Barrett .50 cal just to bring down one enemy.
That they are expensive isn’t a completely valid argument. They’re expensive because they’re restricted enough to keep them in a niche market and not economical to mass produce. If you could go into Gander Mountain or a Bass Pro Shop and buy them off the shelf like scopes the price would be comparable to scopes. You could buy a fully functional inexpensive one for 30 bucks or pay up to a thousand for a premier model. Anyone with even a little mechanical ability can assemble one with off the shelf parts from Lowe’s and Auto Zone for less than 50 dollars. Much less than that if you make or get an adapter to thread an oil filter onto the end of your barrel.
You are absolutely right that noise can be an asset. Our troops in Europe had good reason to be terrified by the sound of the MG42 though and its bite was every bit as bad as its bark. At the time most armies had separate heavy, medium and light machine guns with cyclic rates of fire of ~600 rpm. The MG34/42 was a general purpose machine gun, able to fill all 3 roles and was very widely issued. At squad level with a bipod and a 50 round drum it was a light machine gun, on a tripod with long range sights and 250 round belts it was a heavy machine gun. What made the sound so terrifying was its rate of fire; 1,200rpm.
Quote from “Old Man’s War” from after taining seargent takes a chunk out of a recruit’s hide for gushing over his new hi-tech rifle, thinking he’s going to bust up enemy aliens with impunity.
“There has never been a military in the entire history of the human race that has gone to war equipped with more than the least that it needs to fight its enemy. War is expensive. It costs money and it costs lives and no civilization has an infinite amount of either. So when you fight, you conserve. You use and equip only as much as you have to, never more.”
― John Scalzi, Old Man’s War
Don’t know if it’s true, though. Any comments from soldiers or students of war?
I am surprised no one has mentioned theft. Some soldiers will sell them to civilians, much as they do MREs. (Unlike a rifle, a suppressor can be easily snuck off base.) A system to carefully track them would be very expensive.
That system already exists. MREs are different because once issued they are presumed to be eaten.
It’s not true, or at least not universally so. The US equips for wars it isn’t sure are coming and even for wars it knows aren’t coming, because it has to keep its suppliers in business for the war that is coming.
A problem with Scalzi’s quote is that the speaker presumes the soldiers and their bosses know exactly what the threat is, and therefore can know exactly what they’ll need. That isn’t the case. Lots of crap that the current U.S. Soldier carries into the field isn’t needed at that time, or even during a particular fight. But if they do need it, they really NEED it, and they need it Right. Now.
And what they need changes. All the kit for MOPP-4 is a pain in the ass to use, carry, store, and fight in. Unless the enemy decides to start throwing chemical weapons around, which isn’t something that the soldier gets to know right off the bat.
It’s also inaccurate in that it assumes that the soldier’s life and cost to train them, is of comparable worth to the stuff they use. In the U.S. Army of the last 70 years, that isn’t the case. I think it’s fair to say that the U.S. way of war far prefers spending firepower to lives, if the decision maker is given a choice of choosing between the two.
The US has a volunteer army. I guess this significantly affects the dynamic. How many comparable volunteer armies are there today? In history, before 1945? How would mercenaries affect the calculation?
“Missing Presumed Eaten.” Man, we haven’t had a war that intense for a very long time. 
If that was true, every infantryman in the world would have nothing better than a AK 47. It’s simple, reliable and 'good enough".
However, in actuality, every major modern army issues it’s infantry with something better. Even the Russians have a modernized and upgraded AK , the Chinese have the QBZ-95. The Brits the SA80, the Israelis the TAR-21 , etc.
Note that John Scalzi is a SF writer, and has never served a day in any armed forces.