There was absolutely some key interest in Wolverine back in the day: Len Wein and Dave Cockrum were interested enough in him to make him a part of their All-New X-Men team, Chris Claremont was interested enough in him to keep him around, and then John Byrne was especially interested in him, being a fellow Canadian. So they put the effort into that character. At the same time, they didn’t put the same effort into Banshee, who was written out after a relatively short time. Now, if Cockrum had stayed with the book, he and Chris had intended to write out Wolverine, and if that had happened, maybe Logan would have ended up as a member of the Defenders or something. By that same token, maybe Banshee would be wildly popular today. You just never know.
But that interest begins with the creators on the books. If you try to force somebody to use a character that they have little to no interest in, all you’re going to get is bad comics. It’s also a truism that many of our creators don’t have a whole lot of time for reading each others’ books, as they’re busy working on their own. So they know what’s going on in a general sense, but they probably don’t develop the same love for a brand new character in another title that you might. So it’s not as likely that they’ll bring that character over into their series and use them. This does happen, though, it’s not an absolute–but it is a reason for why this doesn’t happen more often.
We don’t treat any characters like an afterthought, but we also don’t treat every character like a precious flower–we can’t, there simply aren’t enough pages and enough time. Characters get added to the Marvel Universe, and then they either flourish in stories that people do and strike sparks with the audience, or they recede into the background. And then, those characters still turn up from time to time, and get other chances at a shot in the spotlight, depending on who they are. Certainly, nobody on Earth, most especially Stan Lee and Jack Kirby, would ever have thought that a throwaway giant monster that they created in 1960 would be at the center of a major motion picture.
So it can happen to anyone. But it’s not going to happen to everyone.