So you never ask friends to pray for you? If so, why do you need a middleman?
Mary is dead. I don't ask dead people to pray for me.
As has been explained before, there is a big difference between asking friends to pray for you, friends you can speak to directly since they are here on Earth, and asking Mary to pray for you.
She is dead. She is in heaven. Mary can't hear you. The only mediator between God and man is Jesus Christ, her son.
Go through Him. Revere Mary for the great part she played in God's plan of redemption and her obedience to God.
But, don't go to her and ask her to pray for you when you have a direct line to somebody who saved you on the Cross and who is much closer to the Father than Mary.