One thing that probably factors in is that many characters get powers at very certain times - Flash, Green Lantern, Spectre, etc. Kal-El comes to Earth with his powers in place, and its always tempting to want to show them earlier and earlier, or to react against it.
I think this is largely what the post-crisis revamp was about, a reaction to what many saw as an unrealistic history. It would be very easy to argue that perhaps giving a toddler or an infant super powers isn't the smartest thing in the world. I don't like the idea of taking those powers away at a young age but I can see the logic in doing so. The point I was trying to make is that you don't have the option of giving Spiderman or Hulk their powers as children like you do with Superman, some versions do and some versions don't. My question is, should there be one for all time version that has to be universally followed in all forms like there is with the other characters? Peter Parker is always sixteen or seventeen when he gets bit by that radioactive (or in the case of the movie, genetically engineered) spider, Bruce Wayne is always around eight to ten years old when his parents died. With Superman it's easy to pick your favorite version but this creates problems in and of itself when another version comes along that doesn't do the exact same thing. For the most part, you don't have that problem with the other characters.
The one thing I think there is a general consensus on among both the pre and post crisis fanbase is that the early post crisis years were handled poorly. You can't remove Superboy from history and keep the ongoing
Legion series, it just doesn't work. Ditto Dick Grayson as Nightwing. The attitude during the mid eighties was, "Well, we'll sort all that out later..." and it took them two decades to finally do it! That's just irresponsible. Someone should have sorted all this out long before John Byrne set pencil to artboard. You can't have a more "realistic" universe if you leave stuff behind from the previous universe.