Why does a defender use their heads in football?

Answer 1

Only the Goalkeeper can use their hands within the Goal Box. Defenders and Attackers can only use their feet and their heads in the match except when throwing the ball in from the sideline. Attackers must be onside at all times and all players must have studs down in a tackle. Women are allowed to cross their arms to protect their chest but they cannot raise their crossed arms to ricochet the ball which will draw a penalty especially if the ball crosses the goal line.