Having read this whole thread, I now have to ask, do women never pick up guys at their houses for dates? And if they do, would the same rules apply? What about for friends? I sort of get the idea that there's a specific rule that applies only when it is "man picks woman up for Date" that means it's very bad not to come to the door.
I was assuming that if a woman was picking a man up on a date, or if anyone was picking anyone else up on date of whatever combination, the preference of coming to the door would still hold for most people. I personally don't see it as necessary, perhaps because of my apartment living situation with the buzzer and all, but I can follow the idea that it shows eagerness and effort, and it seems logical to me that this would apply to anyone picking up someone that they wanted to impress.
As I said earlier, for me, almost no one comes to the apartment building door unless they actually want to come up to my apartment, like to use my bathroom first--that includes my friends, parents, co-workers, etc.. I am always the one getting picked up because I don't have a car, so I don't have experience on the other side of it, I guess. Most people call me from their cell phones to say they're at the building, and then I come downstairs. They may or may not have gotten out of their cars, depending on the parking situation and the weather. Sometimes people call to say they're "close" and ask me to come down, so they can just briefly pause the car while I get in, and then we drive off.
I grant you some of those things are rather informal for an early date, and I think when in doubt it's probably best to err on the side of caution, that is, getting out of your car and as close to the door as possible--the whole eagerness and effort thing. But, I could see that being impractical at my particular apartment building--when all the parking spots are full, the through-street becomes more of a lane for idling vehicles, especially the food delivery folks, so someone calling from their car to say they were there wouldn't bother me.