I changed a switch in my room with a Lutron dimmer. The switch was sharing the same receptacle as 2 other switches. I pulled it out of the wall and there were 5 wires coming out of it - red, white, two blacks, bare copper. The red and black are part of the switch and the second black is ganged to the other two switches to provide power. The copper is safety ground. Why is there an additional white wire (neutral) going to the switch? Note that it feeds directly into the switch housing and is not wrapped around any external screw. I ended up connecting this white wire to the pigtail with all of the other white neutrals since my dimmer didn't need it.
The other 2 switches in the same spot don't have this hole for the white wire and there isn't another switch for this light. All three switches are functioning properly.
I understand that some smart switches may need neutral to power in existing electronics but this was the original switch which has no intelligent capability.