This has been a problem for far, far, longer than you think. The silver age definitely had it, the golden age probably did, and I wouldn't be surprised if it cropped up in the proto-superhero stories, like Zorro. It's a consequence of having a long-form story where the narrative's status quo isn't allowed to meaningfully change and characters either aren't allowed to die or aren't allowed to stay dead. Recurring antagonists also can have much richer characterization and more complex relationships with the protagonists, which makes writing stories about them more appealing the more often they appear.

The usual trajectory for a new superhero or new incarnation of an existing superhero is to start off with street-level problems, then get a nemesis that has strong ties to those street level problems, then have the dynamic between the two grow in prominence to eclipse all other parts of the plot. The Joker, for instance, always starts off as either a mob boss with a gimmick or a serial killer with a gimmick, not far removed from the mundane crime Batman always starts with, but always winds up with a fixation on Batman and spawns stories designed as some commentary on Batman's no-killing rule. Again and again and again, dozens of times over the decades.

Why? Because the dynamic between the two characters tends to be fascinating and results in audience engagement.