I don't think you've burst any bubble.
There are scenes with body doubles used. Off the top of my head there was a topless sex scene for Jessica Alba's character in one film where they used a body double. Those cases are usually mindlessly obvious because you never see the actresses' face in the same shot as her goodies. Take a read through the thread - there are hardly any scenes posted in here where there aren't shots in the scene that make it clear, the body belongs to the actress in question. The only scene that I recall posted in here where something wasn't exactly what it seemed was the case of the underpants digitally removed - coincidentally, also involving Jessica Alba.
If you want to tell me any of the scenes posted that you think involve body doubles, enlighten us.
Natalie Portman, Brooke Shields and Kate Beckinsale are the only ones from the top of my head that I know of.