Rotoscoping!

Rotoscoping is a technique that dates back to the Fleischer brothers in which live-action figures are cut out and re-drawn. The movement and even features in some cases of the characters tend to be more realistic.
In the mid-1990s, Bob Sabiston, an animator and computer scientist veteran of the MIT Media Lab, developed a computer-assisted "interpolated rotoscoping" process which the director Richard Linklater later employed in the full-length feature films Waking Life (2001) and A Scanner Darkly (2006). Linklater licensed the same proprietary rotoscoping process for the look of both films. Linklater is the first director to use digital rotoscoping to create an entire feature film.
The films are notable for having pushed the genre of animation from a medium that is commonly associated as a childish non reality representing form into a form that has a stronger basis and representation of reality. It brings a bit of realism which gives the medium a bit more credibility and bridges the gap between live action and animation.
My interest in this, is the questions of why is it that we need some form of reality to achieve credibility? Why Can't animation in its various forms, from traditional illustrations to computer generated form, without the obvious references to reality be seen as a liable and serious medium.
What is it about a moving illustration that has deemed it "childish"?
There are many animation that are serious, but in the mainstream and even in the history of animation it seems that it has been set as a device centered mainly on the portrayal of the silly, innocent and mindless amusement.
Is it something about the way we perceive human motions, speech, and character in reality that prevents us from accepting animation which is comprised of fabricated realms and simulated realities as truth?