By common place I meant by the units that can afford them. If they can get them, they do. I will update the text to reflect my intentions. Thank you for upvoting. This is a huge pet peeve of mine.

Subsonic ammunition is highly uncommon in military use. Suppressors are normally used with standard ammunition. You are right: there is no reason not to use a suppressor if you have one available; just like real life. Suppressors have no negative effects on the projectile. Weight, length, and cost are the only detracting factors.

In short, the are not 'overpowered'. This game is about realism, not balancing. In fact they are underpowered, as they currently lower damage and range. This is highly unrealistic and I have a ticket for that.

This is realistic. Normally people have to purchase tall sights specifically meant for use with a suppressor. The new sights are less than ideal due to the increased height over bore.