Under the heading "Examples in Popular Culture"

According to the theory, suspension of disbelief is an essential ingredient for any kind of storytelling. With any film, the viewer has to ignore the reality that they are viewing a two-dimensional moving image on a screen and temporarily accept it as reality in order to be entertained. Black & White films provide an obvious early example that audiences are willing to suspend disbelief, no matter how "unreal" the images appear, for the sake of entertainment. Except in the case of color-blindness, no one viewing these films sees the real world without color, but they are still willing to suspend disbelief and accept the images in order to be entertained. The advent of films in color has not changed the audience acceptance of Black & White films.

Your point about fairy tales is confusing "suspension of disbelief" and "belief". A suspension of disbelief occurs, not when you convince yourself that something is true, but you ignore its unreality because the story is engaging you somehow. By your standard, one would have to actually believe in fairy tales to suspend disbelief.

As a result, an impediment to suspension of disbelief occurs any time additional elements are added into a story that are implausible. If you have been reading the Martin series, for example, you have already come to terms with a fake world, magic, dragons, a giant wall of ice and some weird undead on the other side and odd seasonal shifts. If, however, in Book V (if it ever gets written) Martin were to add space aliens, he would lose readers because the addition, done in the way it was, was too large of an impediment for people to continue suspending their disbelief for the purpose of enjoying the story. That point would stick out and remind them.

Suspension of disbelief is essential to ALL fiction.