That doesn’t mean they don’t have sex, though. Celibacy is about behavior, while sexual orientation is about attraction. Anyone of any orientation can be celibate, and anyone of any orientation can sleep with someone they’re not attracted to. Many aces are sex-repulsed, but others do do it. In some cases, aces are personally indifferent to sex, but want to compromise with romantic partners who are allosexual (not asexual). Others want sex for emotional—not physical—reasons, to feel close to someone they love.
To the greater world, aces like Rachel are often seen as unhealthy, abnormal, possibly sick. For example, the Diagnostic and Statistical Manual of Mental Disorders, the “bible” of psychological disorders in the US, includes low (or hypoactive) sexual desire as a psychiatric disorder and companies like Valeant Pharmaceuticals have tried to cash in by offering dubious libido-enhancing drugs. To aces, however, their experiences are simply part of human variation, and it is as natural to have a high sex drive as it is to have a low one, or none at all. From the ace perspective, having a low sex drive isn’t a psychiatric disorder any more than being gay is (homosexuality was also in the DSM until the 1970s).