Technically I beleive the only efficient systems are those where it is known a priori who employs birth control. That basically means it must be the responsibility of one sex or both. I agree with you: both sexes may be overkill but is the only fair option.
I don't get it - what does that kind of fairness buy you or society? If it's enough when one side takes contraceptives, what logic argument is there that the other side must do the same? Economically (time, resources, even environmentally; the pill and condoms eventually end up in our water or the sea) this does not make sense.
Ah yes should not have forgotten redundancy being good. Fairness is obvious: cost of procedures, risk of side effects, time spent in operation, etc is born by both parties.
