Actually, a good question Snaark.
Suppressors affect the internal and therefore external/terminal ballistics of the firearm quite a bit.
One key thing that normally happens, is that you start to run sub-sonic ammo thru them which doesn't break the sound barrier to keep it suppressed. This means a reduced powder load, adjustments to the grain (weight) of the bullet and ballistic performance.
Simple answer, if you screw on a suppressor and start running regular ammo thru it, it won't be as silent as they are supposed to be and will impact the performance of your weapons. Some of them need to be cleaned a lot too.
One company I used to deal with (Advanced Armament) used to have a quiet marketing sticker with the 3 Monkeys:
See No Evil (Hands over eyes)
Speak No Evil (Hands over Mouth)
Hear No Evil (Monkey waving a AAC Suppressed Pistol over his head)
"Those who beat their swords into plowshares, inevitably wind up plowing for people with swords".
Jefe: well into a 12 pack of LaBatts Blue (AKA "BlueDevils"