It’s interesting to compare the treatment of safer sex in Original Recipe 90210 to on something like, say, Gossip Girl. Or, indeed, general conversations that we (by which I mean “I”) have with our friends.
I mean, could you imagine Dan saying to Blair in this scene, “You used a condom every time. Right?” Or Blair telling Dan she and Chuck had both been tested for STIs? We all know damn well they didn’t.
See also: this article.