ValentineWiggin wrote:
"Why treat the sexes differently?"
"Herp derp it's just courtesy!"
"...huh?"
"Manners!"
"...but why treat people differently based on their sex?"
"Gawd, who carez anyway? Get a life."

I think Valentine makes some excellent points here.
My thoughts: There's nothing really wrong with old-fashioned manners. Why do I open the door for my wife? Because she is the Queen of my household and deserves to be treated like royalty. It's just plain NICE to do things for people you respect, and I don't believe that she as a lady has any similar reciprocal obligation to me.
I am, of course, the King of the household, and as such I enjoy a certain amount of executive privilege. I'm the tie-breaker and veto power of the house. But, if you really want to be a good domestic politician, it does one well to recognize that tie-breaking and veto power are best used sparingly. I'm not a tyrant, after all. My wife is the "chief breadwinner," so she hold considerable power in her own right that, more often than not, I defer to her when it comes to decision-making. I recognize, also, her brilliance in all things economic and domestic. To go against my wife on something means I have strong convictions on something. These are the rare times that I'm right and I KNOW I'm right. It might make her angry if I "pull rank," but she also recognizes that I'm also 50% of this relationship and my opinions count for something, too.
The erosion of traditional rules of politeness between men and woman, I think, is mostly due to hardline feminism and postmodern confusion and ambiguity as to exactly what gender roles are or are supposed to be. If a woman is genuinely offended by a guy opening a door for her or feels her independence is threatened by such an action, she may simply say so and the guy never has to open a door again. "Just being nice" means respecting the wishes of a woman either way--it would be impolite to do those things if it bothers her. So, for me, holding a door becomes something that is helpful or a convenience to anybody walking through that door. I might open a door for my wife and my children, and if someone is behind me, I'll hold it open at least long enough for them to catch it. One thing I really HATE is when someone sees me coming just a step or two behind them and closes the door in my face. It's not merely socially coarse. It's flat-out inconsiderate. People in general tend to like and respect you more when you're helpful and, at the least, recognize and validate their presence.
And so if a man enjoys the presence of a woman, if thinks of her as being special and wants her to feel that she is special to and respected by someone, what is really wrong with being nice and treating her like royalty? We aren't able to lavish food and luxury on women 24/7/365. But it costs a man absolutely nothing to open a car door and offer a hand so she's not inconvenienced by having to CLIMB out of the car. If it's a problem, I won't do it. But I don't see why it's necessary that such niceties in the context of current culture and society are really just actualizations of an old-fashioned view of one sex being "weaker" than another. I think a lot of people just want to be nice.
This may be a stretch, but in the context of current culture/society, there may be some practical applications here as well. When entering a building, a woman and/or children are at their most vulnerable. A man, typically having more muscle mass and thus more brute strength, is an effective rear guard and less likely a target for kidnapping or rape. An attacker at least has to think twice about it when a man is involved. So rather than being an oppressive institution, it's an instrument of security. Maybe/maybe not. The point being I can see at least one possible good reason for keeping.