Why do people continue citing the Rosenbaum study as proof that abstinence education doesn't work?

It would be interesting to see some more stats on number of sexual encounters by abstinence-only teaching/none-or-other methods. I mean, per Wikipedia, pregnancy rates using only a condom are on average the worst at 18%; a condom user (well, condom user’s partner) would have to have sex 8 more times than someone who has a single, non-protected encounter to be at the same risk rate. HIV/AIDs infection rate lowest reduction is 80%, so that’s roughly the same sort of difference. (I think, anyway; statistics are really not my strong suit). Which is a worrying figure, especially compared to the numbers you’ve quoted.