Why are QB's wearing a dot in the center rear of their helmet? No other players seem to be doing this.?

Answer 1

The dot represents the helmet that has the radio receiver in it that is connected to the coach calling the plays; it is there so that the officials can be sure only one player has radio capability on the field at a time.

Answer 2

Microphones are placed in the helmet, in order for the QB to get the play called accurately. Take into the account of how loud the stadiums are.

Answer 3

Players who have the green dot on the rear of their helmet are the players who have microphones in their helmet