The reasoning behind almost every custom is essentially practical.
Women sometimes wear skirts, dresses, and coats that get caught in coach doors. To protect the fabric and the cost that went into buying the garment, men make sure that the women are seated with all objects free of the jamb. Same goes for the seat belt or other items that women often leave dangling. You wouldn't want to get out to your car and find the battery dead because the door was ajar and the dome light was on, would you?
Women are often on the period, premenstrual, pregnant, postpartum, menopausal, in hormonal disarray, or carrying children, which makes them more prone to be dizzy and weak when getting up and down. Women are easily distracted by their own emotions, and don't close doors properly before getting under way -- which is dangerous for her. You protect the pvssy that you enjoy fvcking just as you protect the uterus that carries your son and the breasts that feed your son.
Besides, just as I said, if she opens her own door, the lawn mower, the tree trimmer, the neighbor, the azzhole blaring his stereo in the parking lot, the homeless guy who just stole some of your nice clothes from the dryer -- they all get the clear message that she wants them to come and get her the minute they see your azz leave.
Be practical about it. Stop thinking in the male-female warfare mindset that feminists got your brain screwed into -- or in the false dilemma of sissyboy v. thug which is nothing but feminism rewritten in words that are supposed to be appealing to the claymation model of (eww! breeders!) that feminists despise.
__________________
I am not her man. She can't stand the thought of me touching her. She's dripping with other men's semen. She is ashamed to be seen with me. She never misses an opportunity to disrespect me. Everything I do is wrong. I am the problem. She got what she wanted from me. She says "I hate you so much I could kill you." Going away forever will make her happy again. So I'm leaving her to her pumped-and-dumped lifestyle and leaving her bastard child fatherless. I'd be better off with no woman at all than wasting another second thinking about her. I learned from my mistakes and the next relationship will be done with planning for my happiness.