But they can use the rhythm method to help prevent unwanted pregnancy?
It's call being realistic. One method works much better.
Depends on who is using either method. The condom works only if it is uses according to instructions, and for most people the instruction put a responsibility on the user that is too much for them to bear. It was, after all, a devise developed for prostitutes, and prostitues generall don't think of sex as a religious act, as did so many flower children. The number of abortions attests to the "efficency" of condoms used by amateurs.