Yea, the world could use some more courtesy these days couldn't it?
I think it's because the self-restraint involved in being polite is incorrectly fiewed as a lack of ability rather than a refusal to exercise that ability. Sure I could ogle every set of boobs that came by but if I'm there with a girl than it would be impolite to give her less attention than she deserves, and if ogling other women is the attention she deserves than why would I be there with her in the first place?
Sadly, failure to act like a horny dumbass is interpreted as being an impotent twit. Not all guys think about naked women and having sex all the time, despite what many would have you think(no, I'm not gay). Sometimes, I'd really rather just have a nice conversation, or watch a movie. But since I don't go out 'drinking and wenching'('s how I think of it anyways) I'm viewed as a loser with no-life. Can't really blame people for being cynics when they act decently and get mocked for it.
So no, all the gentlemen are not dead; they're just unpopular.
{This would work well as a poll}
Edit: and specifficly on the note of courtesy; I have yet to find anything that makes me feel quite as good as holding a door for people. It's one of the few things I do and it actually makes me feel like a good person.