That AND the less evolved nature of most characters.

Everyone and their grandma can make a dio around Snake Eyes and Storm Shadow's evolved affair. They are the Wolverine and Sabretooth of Marvel, or the Batman and Superman of DC

... With others of repute filling in the voids of said main characters of either side.

Hate to hit this again, but over on GeneralJoes, there was a HUGE ongoing dio concerning Hit n' Run! Absolutely FANTASTIC, without centering on any main character, in fact, the MAIN character only had ONE SINGLE RELEASE! And that was towards the end of what I consider the "hard" run. (Before neon, and multiple repaints of old Joes)

The author took a VERY background character and centered a fabulous story around him. Making that character HUMAN, the way Marvel, DC, and any others have done with their top SELLS.

And THAT ALONE is what I love about the Joe-Verse. Any and every character involved has a creditable backstory...and better yet, there's HUNDREDS of them. Countless numbers of stories!