Because in their philosophy sex serves a purpose (procreation and the deepening of the marital union).
Anything that doesn’t support those two aims (contraception, abortion, gay marriage, pornography etc.) is therefore immoral but there’s nothing wrong with sex in its ‘proper’ context.
It is already outlawed in any practical mean. There is no proper way to consent. If participant changes their mind ten years latter, good luck at court!
Anything that doesn’t support those two aims (contraception, abortion, gay marriage, pornography etc.) is therefore immoral but there’s nothing wrong with sex in its ‘proper’ context.