not as old as the OP, but up there, and they should be pretty obvious: older workers are in completely different phases of their life, share few of the social aspects that younger workers find important or critical, and (lets face it) we're typically in a different place physically.
So much of career advancement is shared social & cultural values and norms, and we're out of sync with a workforce that skews significantly younger.
There's also a great deal of anger at my generation (and the one before). Not all of it is misplaced.
But I won't get into it. Anger breeds anger. I am not stereotypical anything. Most folks, here, seem to develop an entire personal narrative of others that post here, based on one or two posts. I have the habit of doing that, as well, but I deliberately ignore it, and explore the HN profiles of folks that interest me (or attack me). I generally find out that we actually have a lot in common. Sometimes, I have even made friends with people that started off, hating my guts.
I'm a weirdo. I don't really fit any templates out there -even good ones. If people get past the age thing, then they generally seem to think that I'm "hiding" something, or being an overbearing ass.
Might have a point. My ass has become more overbearing, as I have gotten older, and I believe that most folks prefer that I keep it hidden. It's not pretty, when I show my ass.
I'd be interested in hearing what you think these personal and emotional factors are.