Most people who are into Goth absolutely love both cemeteries and churches for trysts like that. Even for normies the forbidden is always more exciting when it comes to sex and both of those settings are about as forbidden as possible for anyone with a religious background (either loving or resenting it). I would guess that the number of sexual encounters in houses of religion would rival pretty much anywhere other than hotel rooms because of this, but most of that would be vanilla couples doing "normal" things in a place that is just more exciting.

However, in every organized religion (irregardless of the actual teachings of the religious text) there is a puritanical streak that at some level is anti-sex (or in the case of some cults pro-sex but in a very specific and prescriptive way). For that part of the congregation that are hard-core, the thought of any sexual activity that is not specifically prescribed by that religious authority in a completely private setting is dirty/bad in some way in general, so doing that in a place that is religiously sacred to them is offensive.

As a side note, I just drove past a sign on someone's lawn yesterday that said "The wages of sin is death" (reference is Romans 6:23 from some unknown writer supposedly inspired by god).. and I thought, well... isn't the wages of being "good" also death? I mean, the holy prophet James Douglas Morrison wrote "No One Here Gets Out Alive" (reference is Waiting for the Sun 2:5).

My questions, like yours, are Why should I care about your view of sin Mr. religious zealot anti-sex person and why should anyone consider your religious text, and interpretation of such, as any "better" than mine from a legal/ethical/moral standpoint?