I don't understand this aversion. I occasionally saw my parents having sex when I was a kid. It was no big deal. I knew that they were doing it more often than I saw it and I knew how I got there.
Being from mainstream suburban US culture, I know only one family in which the members had sex freely in front of the others. The kids grew up seeing their parents have sex, and they had sex without being freaked out about closing doors and being quiet. It was just a natural part of life for them. Why isn't it like that for all of us?
The majority of humans, historically speaking, must surely have had sex in front of their kids. Most people have lived in one-room dwellings, and I doubt they abstained. They probably had much healthier views on human sexuality than that of American prurience. People assert that kids would be damaged by such exposure, but I want to know how and why they would, and further, why the other people with such experiences were not. But no one provides a respectable answer.
Shouldn't we be striving in this way to free ourselves from the dogmatic and limiting inhibition with which we are culturally programmed given that there is no plausible damage and substantial possible benefit? The idea of having sex in front of my kids makes me uncomfortable. But contributing to the sense of taboo that my kids will know because of not being open about sex seems irresponsible.
There it is...hiding sex from your kids is an act of irresponsible parenting.
But like most other people I know, that's what I'm doing. Maybe I can learn to be strong enough to overcome the discomfort.