Why do you have to throw a sideline ball with your hands above your head in a football match?

After all, it is football, and the role of the hand should be weakened.

To throw a sideline ball, you must raise your hands above your head and not jump.

The foul ball is thrown with one hand, and some teams specially invite people who can't play football but have strong arms to throw the foul ball. This is not conducive to the development of football, so we throw the ball with both hands instead.