Long before Superman's life story had been fleshed out, the first snapshot origin of Batman appeared in Detective Comics #33. In the case of Bruce Wayne, the death of his parents was not just a haphazard detail, but foundational in the psychology of the character, who vowed war on crime precisely in response to the murder of his parents taking place in front of his very eyes.
In the wave of superheroes who followed, the typical hero is first shown as an adult man, and there is simply no reference to his ancestors. An exception is Doctor Fate, who was first said to have been created as an adult, having never been a child. In a retcon, a later origin had him obtain his powers after the achingly tragic death of his father. And when Batman acquired his sidekick Robin -- one of the most enduring of those early characters -- their lifelong association began precisely upon the occasion of the deaths of Dick Grayson's parents. To a man, the earliest superheroes had no fathers, either because the stories did not mention them, or because their fathers had died. This tendency generally held true with superheroes created by other companies (Billy Batson and Peter Parker were both orphans), and when Hal Jordan was given a more detailed backstory long after his creation, he too became a man who was shaped by the early death of his father. We may also note that Wonder Woman, for very different reasons, never had a father at all. Whether or not Jerry Siegel started the ball rolling, it is clear that a number of later creators took the inspiration and found it compelling -- almost unavoidable.
By and large, superheroes have been without families -- particularly without parents, and most especially without fathers. And while this is a fact of many real people's lives, it is not nearly so common in the world as it is for superheroes. As a variant on the typical pattern, maybe as a token "normal" superhero, Barry Allen was bestowed, though not at at the time of his creation, with a wife and with living parents, a living father whose name was Barry's middle name. But his parents were initially margin characters, little more than props with a couple of speech balloons when they were introduced in Flash #126. And in time, Barry's world came tumbling down, with the death of Iris, and then his own death which was followed, the next Flash series mentioned in passing, by the deaths of his parents, too. In the current Barry Allen revival, his mother has been retroactively (perhaps, because time manipulation was involved, not permanently) killed by the Reverse Flash, and Henry Allen died in prison as a result.
Comics are fond of imagining things otherwise, and so dead fathers have lived again. Superman has seen the Kents as part of his adult life in the post-Byrne continuity and on the television series Lois and Clark. But writers have also portrayed living parents as a symptom of dystopia, with the whole world going wrong as seen in glimpses in Alan Moore's For The Man Who Has Everything, Jeph Loeb's Absolute Power, and Grant Morrison's Last Rites. Stories like these make out that it is not just window dressing that the heroes have lost their fathers, but essential, an unpleasant fact that makes the hero, and therefore the world, as they need to be.
I've discussed before the family-less nature of Batman before and proposed that it probably excludes him from appeal on the highest levels of popular serial drama. While Smallville gives young Clark Kent people filling relatively normal roles around his abnormal life (and yet, his two fathers also died), Batman is inherently a man without a wife or parents, and so he appeals to the audiences of animated shows targeting more or less the demographic that comics target. As The Dark Knight showed, all the world may want to look into Batman's life for a couple of hours every three years, but it's not a world that every demographic wants to visit weekly.
Do superheroes really need to be fatherless? Does a father inherently belittle the son, shadowing his brilliance? Sherlock Holmes had no father, nor did Gilgamesh. Were the creators of Batman lazy in copying Siegel's fatherless Superman, and the creators of Hal Jordan following suit? Is this pattern a matter of necessity? Clearly, it has been integrated irretrievably into the Batman story, but Hal Jordan and Barry Allen have lighter characters, with origins bestowed upon them from beyond. Can a mainstream superhero have a father? Why don't writers think so?