Remember "Romancing the Stone"? When I first watched it years ago, I remember another writer friend of mine saying that he wished Michael Douglas' character (Jack Colton) could've had some heroic theme music. I thought about that for a moment and pointed out that he didn't need it because he wasn't really a hero. Kathleen Turner's character (Joan Wilder) wanted him to be, but what she got was the realistic version of an adventurous man who was nowhere near the romanticized hero she wanted. He was self-centered and money-motivated. That was the point of the situation. They both had to be shaken up a bit. He had to polish his act and rise to challenges that weren't in his selfish "best interest". She had to get her head out of the clouds and learn to not measure a real man by an idealized standard.
In realms of adventure, fantasy, thrillers and certainly superheroes, heroes and heroines are often cast as "larger than life" figures. As such, their motivations are best not subjected to overanalysis by mortal kind.
In basic terms, the hero is a fool saddled with self-destructive impulses who's managed to channel them in a socially acceptable manner. Don't get me wrong, I love a hero and I know lots of us do. We respect and revere heroes. We crave them so much that we seek them out. Still, the actions of heroes run contrary to the instinct for survival and genetic preservation that we're supposed come with as factory-standard equipment. To run into a burning building while others are running out isn't considered the hallmark of sanity. Likewise, neither is facing down a hail of bullets or standing ground against overwhelming opposition. Putting one's own life at risk for the sake of a single other life is not a logical trade (especially one who is weaker and of less obvious worth to the community gene pool), but try telling that to a hero. As far as an audience goes, individuals will usually feel that heroes belong somewhere on a spectrum between being celebrated or being medicated.
To look at heroic exploits through the lens of realism distorts the remarkable into appearing ridiculous in the eyes of the mundane observer. Without the suspension of disbelief, heroism is readily mocked. A man dressed as a bat becomes a misguided socialite with psychological issues in need of therapy. An altruistic alien superhuman is reduced to an overzealous, boy scout in silly tights. James Bond would just seem like an overdressed maverick mysoginist making his colleagues feel inadequate even while sitting in the waiting room for the therapy session following Bruce Wayne's. Peel away at too many layers of your superman, dig too deep beneath the surface, and you'll leave yourself with just a man. Who really wants a naked Santa standing in the living room explaining himself? Nobody, that's who. (Now, let's all try to purge that particular image.)
Readers aren't seeking pure realism now anymore than they did in the days when the "tall tale" reigned. Scrutiny of the motivation behind great deeds reduces them to forms of mere human behavior. Audiences are already faced with realism and its trappings every waking moment. It surrounds them. When they seek out the extraordinary, giving them less is a disappointment. If they could live the deeds of heroes on their own, they wouldn't be immersing themselves in movies, comics and novels. Don't berate them for seeking the fantastic. Give them something fantastic.
What's your favorite form of escapist, fantastic entertainment?