Apples and oranges Tiffy. Granted, the average issue weapon is moving closer toward the SCHV (Small Caliber High Velocity) ideal. SMG's on the other hand are evolving toward being a specialists weapon. Police, and anti terrorist useage, where one does not need massive penetration (shooting innocents on the other side of a wall due to overpenetration is bad..) Also, the move toward supressors in A/T use, and police is to ease communication. A mag of 9x19 in a small room will give one a serious bit of tinitus for more than a day.
Yes, supressors are expensive. This is due to the materials used which negate two of your points. Weight, and fragility. Just as firearms have evolved, so have supressors. Case in point? Early Sionics M-16 supressors were not able to handle more than a mag's worth of full auto fire before needing service. Current AWC M-16 cans just get warmer, suffering no damage.(the bore will suffer before the can) Reasons are the ability to computer generate gas flow within a supressor, as well as the collapse of the soviet union (Titanium became much cheaper) I've dealt with a M-16 supressor that reduces the report to that of a .22LR, and upon direction of the agent, fired literally nine 30 round magazines through it. No change in sound signature and the '16 seemed to put bullets where I desired from 25 to 300 odd yards. I was worried more for the rifle, than the can at this point. Really changed my perception of F/A supressors. Hell, I've seen supressors for ANM2.50 BMG's.
Regarding the can affecting shot placement, or range, I'll counter with "Sometimes" . On a long range, precision rifle a supressor will affect the shot, due to altering barrel harmonics, as well as the base gas flow post bore.
In a circumstance such as this, the range of the weapon itself would prove to be more of a benefit than a full supressor. At best, a tuned moderator would be all I'd consider.
However I'm referring to projectiles fired from short stiff barrels, which are already travelling below the speed of sound. Range would not be an issue in house to house, or room clearing.
Again, I'm not predicting SSMG's turning up in the hands of the basic grunt, instead they'll be in the hands of specialists.
OCIW- Yes. They are. All the better to supress the noise.