This is a post of mine I rediscovered from another site in which I responded to the question: "If you had to eliminate either sex or violence from fiction, which would you eliminate?" This being a comic book site, the overwhelming majority of responses was to strike away sex because "porn is boring" and "violence is awesome."
However, I gave this some thought and came up with what I thought was a rather good point.
Then the thread got locked and deleted some twenty minutes later. Thank god I saved a back up:
Violence is fun, but it can be there for eye candy as easily as sex. However, I agree that it is often more important to plot than sex, because it is more applicable and understandable to human experience, regardless of age and maturity. Sex, however, requires a level of maturity to understand as well as appreciate the importance of in a work. Sex is more complex in terms of audience reaction than violence, even though violence may be more complex in execution.
I would not get rid of either, honestly.
I would note, however, that I think sex is being too easily dismissed here. Sex as a means of expressing characterization is not quite as limited as you think. Sexual desires, not just gender preference, but kinks and fetishes can be very telling of a person's deeper personality traits, how they try to present themselves to others, deal with relationships in general, and how they really feel once the mask is stripped away by intense intimacy. Sex, as much as violence, can be a means of torture and torment. Sex can sometimes save a person from themselves and for some can jump start a move to maturity. Sex can be as destructive and it can heal. There's a lot more to sex than just describing in various ways how Tab A slides into Slot B.
The problem is that most people don't know how to use sex well for a story. Of course, I would argue most people don't know how to use violence well, either.
There are many violent action scenes that could be cut down to simply one or two hits, and serve the plot just as well as making a five minute spaz fest. Anything more than the victory blow is often times really just padding, and for action heavy shows that continuously see saw back and forth over who gets the upper hand, it can get ridiculous. This can be a notable problem in movies with advanced special effects showing HUGE battle scenes with tons of shit going on. Eventually, it all blurs out, and you just want to get on with the damn story already.
Sex, likewise, can be glossed over and implied, and often, its better left that way. The couple kisses, and the screen fades the black, and that's all you really need. Due to sex preferences being much more varied than violence, its more effective to use the imagination so the reader can fill in the blanks themselves. When you go ahead and do the full sex scene anyway, it, just like an over the top violence fest, is just there for eye candy.
You might say some fights are really about the verbal argument and battle of wills between the two combatants as much as it is the guns blazing and fists striking, and therefore its important to show the details. But sex can be used this way just as well, and the most effective sex scenes do emphasize the characterization behind the action, be it a couple simply coming together after struggling with intimacy issues or a dominant trying to make someone into their submissive.