That's because you're looking at it from the tail end. Smallville started at a time before superhero movies ruled the box office, when comic-book-based projects were still considered something of a disreputable niche. So the original intention of the series was to reinvent the Clark Kent story without any comic-booky elements at all -- "no flights, no tights" -- and present it in a form palatable to mainstream audiences, something more in the vein of Dawson's Creek or Roswell. The same principle as the same network's short-lived Tarzan adaptation that was reinvented as a New York City detective drama -- take the characters and premise, but strip away all the genre elements in favor of something more conventional and crowd-pleasing. The express purpose was to transform the concept into something palatable to audiences who had no interest whatsoever in superhero comics, who didn't even know the show was inspired by Superman (and there were indeed fans of the show who did not know that).
But as Smallville went on, it changed massively in its approach. It ran so long that it drained its original premise dry, so it had to draw more ideas from the comics in order to sustain itself. And by that point, superhero movies had become more popular and respectable anyway, so the show didn't have to try as hard to conceal its comic-book roots. So in retrospect, people look at it as a heavily comics-influenced show. But I'm talking about the original intention of the show in its early seasons, when it aggressively avoided anything that even hinted at superhero comics.