Depends on what the scene is for and what sort of book it is otherwise.
To take an example I expect we are all familiar with, I do not think the bondage scene in Death Masks would have worked offstage, because of the emotional weight attached and the specific things going on there.
Myself, I tend not to write explicit sex scenes because the moments of transition in realtionships between people that I am interested in are more about becoming friends, becoming confident in being found attractive, becoming closer, making decisions... once you know where the scene is going to go, there's no point in putting it in.
There are people, fictitious and real, for whom having sex with someone is a world-changing and relationship-defining experience. There are other people, fictitious and real, for whom it's something nice to do of an afternoon when it's raining and there's nothing decent in the cinema. I tend to write about friendships and relationships within which it's closer to the second once the friendship and relationship are solid, partly because it's closer to how I work myself so easier to get right, and partly because I have very little time for a lot of aspects of how romance is generally supposed to work in Western culture and have no desire to wite a book promoting them.
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