I know many women who admit they "fall in love" anytime they hear a low bass. They might marry a tenor and never cheat on them, but every time their hear a low bass their heart flutters. Men know/see this and so tenors become less interested since their higher voices don't get the women (there are plenty of other ways they have).
I don't know how much this is a factor, but...
This is now my favorite benign conspiracy/cause of the lack of tenors!
Damn those big-voiced basses — they're stealing all our love interests :p
Anecdotal I guess, but when I was in a high school choir, I loathed that my teacher assigned me to the tenor section. It did not fit with the image of myself that the high school version of me held in my head; "a man should be a baritone or bass after puberty!"
I liked choir and stayed in it for all four years, but I was never particularly good at it so what the hell did I know anyway.