When something runs counter to what fans expect, the fallout can be quite severe. If you want a clear example of this, look at the furor over the revelation that Captain America has always been a Hydra agent. People have a clear idea who their heroes are and what they represent. Something must be working, as the character's been going strong for 55 years, with no signs of slowing down anytime soon. That's not to say the series doesn't go to dark places occasionally, but it's mostly kept from getting too dark and brooding for its own good. In general, the Spider-Man comics hang out on the lighter end of the comic book spectrum.
We're acutely away of his reason for becoming a hero thanks to the famous “With great power there must also come great responsibility” mantra, and it's been Peter's guiding light throughout his web-slinging career. Perhaps one of the key elements to Peter Parker's popularity is the fact that he's such a clearly defined character. Starting from humble beginnings in Amazing Fantasy #15 in 1962, Stan Lee and Steve Ditko's Spider-Man grew to be one of the most iconic and beloved heroes of all time.
