Self-Pleasure in Anime

[http://www.otakunovideo.net/wp-content/uploads/2010/10/yosuga-no-sora-01-300x168.jpg|300x168px|Yosuga no Sora]

Josh mentions in his review of Yosuga no Sora's first episode that he was surprised to see a scene of female masturbation in that anime. I haven't seen the episode, so I can't comment on that specifically, but he brings up an interesting point:

For all of the sexuality in anime, how often does sex actually occur?

We see lots of bouncing breasts and panty flashes. But it's never consummated. I can only think of a handful of non-hentai anime in which the main characters clearly have sex:

 
 * ef -- a tale of memories
 * Infinite Ryvius
 * ''Mind Game
 * Neon Genesis Evangelion (Misato)
 * ''Now and Then, Here and There
 * Paranoia Agent
 * Please Teacher
 * serial experiments lain

There are other edge cases, like Gundam Seed, where sex is strongly implied.

Even the more adult-oriented anime--Ghost in the Shell, Battle Angel, Metropolis, Texhnolyze--at most implies sexuality.

Why is that? If the medium is so saturated with sexuality, shouldn't it address the reality and consequences thereof?