Why does the comic book industry have a history of short-changing creators?

A couple of weeks ago, Disney opened an old wound in the comic book community by releasing their new Stan Lee documentary. On the surface, a documentary about one of the most charismatic figures in the history of the funny book business, who made it his life's mission to proselytize for the medium, shouldn't have ruffled the feathers of comic fans and industry professionals. However, Disney's documentary decided to minimize the contribution of Lee's co-creators, specifically Jack "The King" Kirby, who was responsible for the lion's share of Marvel's early creative. 

And while it's embarrassing to watch a company like Disney, which has made a fortune off Kirby's contribution to the comic book medium, discount the role he played in Stan Lee and Marvel's collective legacy, they're not first, as the behavior has been a common practice well before the modern superhero movie boom. 

In the video linked above, the YouTuber Matttt explains how frequently comic book creators have been short-changed by the very publishers they helped make rich.