It’s a lack of courtesy and it’s trashy. Most weddings have children and most weddings don’t really have “bedrooms” for people to have sex in so the sex is probably done sneakily at the venue which can get the wedded couple in trouble since they are generally the ones that book it. If it’s somewhere like in their car, it’s just straight up trashy. Like you couldn’t wait to just get home to do that? You were supposed to come to the wedding to celebrate my marriage, not use it as a brothel