Because not every gun is designed to plug in a silencer.
Why? The only reason for that is as a poor excuse for this.
There is no reason for their not to be standard DNI adaptors on the gun to control accessories (laser lights, external smart link, sliencers, etc.). Have four years really managed to drive all those off the street?
That's a pretty bad ret-con for balancing that never needed to be done.
As for recharging, that's just as much of a new issue that was just created. Contacts run just fine in 4E. So do external smart links, etc. Why is wireless suddenly needed to recharge these things when 4 years ago there were powerful enough batteries that they didn't even have a lifetime listed.
I fail to see how the silencer can't run audio on a battery when contacts are (or at least were able to 4 years ago) run visual data on a battery that had to be minuscule.
Again, it's just another poor excuse to edge us toward wireless over DNI. It ignores the setting's history.