OK general question...

Rules are placed in sports so that both teams play under the same conditions and therefore the better/luckier team can claim a victory based solely on the play.

Additionally rules are in place to create/foment better games.

Therefore when a governing body creates a set of rules it must believe that they are doing so for the betterment of the game.

Can someone please explain to me why a double yellow/soft red will make the game better? Or any of the other rules for that matter?

I do not understand the arm-chest protection for females for chest traps (in walls I see no issue) no female player in the higher levels does this.
There is a governing body that already created a set of rules for youth games why not follow them?