As with all things, good manners must be predicated on good sense. If a woman is holding a bunch of packages and a man does not open the door for her, he is a behaima. If we did not bring our bochurim up to believe there is something untzniusdig about opening a car door for their date, they would never view it as such, on their own. It is when you put certain ideas into someone’s head that those ideas take root.
There is a world of difference between saying that something is assur (re: walking behind a woman, even one’s own wife) and saying it is not proper or “unbecoming.” In those days, across the board, it really was not done that any woman preceded her husband. The “little woman” knew her place (I am not a woman’s libber, by the way, believe it or nto I am very old-fashioned). So in that time, it takeh would have been very unbecoming for a man to walk behind his wife. Even the non-Jews held by this idea, with the exception of the very upper echelons of the British elite, who prided themselves on their drawing-room manners. And even then, there were instances where a woman would never preceed her husband, lord of the manor.
We do not live in a day and age where woman are regarded as chattel. If something is assur it is assur. But if it is less halachic and more the OPINION that it is “not becoming,” the notion of what is becoming DOES change with time. At one time it was not becoming for women to vote. At one time, it was not becoming for women to work outside the home. (Oh wait, I guess things DO change when it suits the ideology of the person who wants to see that change effected for his own purposes). The point is, halacha is halacha, and what is considered proper sometimes changes within the context of the times in which we live. And i am not suggesting for one minute that this means we should do prutzadig things. Opening a door for a lady should not be such a gedilla. Sometimes I think men hold onto these “laws” (with righteous indignation) because it is a good excuse to continue their boorish behavior, and use the Torah to justify it.
PS – My husband STILL opens the car door for me after 32 years.