Why does Marvel need to introduce the X-Men across three films? Did Fox need three movies to introduce the X-Men before 1999's X-Men? Did Stan and Jack introduce the Original Five with cameos across Amazing Spider-Man and Fantastic Four back in 1963? Did Len Wein and Dave Cockrum introduce the new X-Men across multiple comics before Giant Size? No, no, and also no. Give the audience some credit. If they're dropped fresh into a new iteration of the Xavier School, they are going to manage.
I need to catch up from pages 1315 onward, but wanted to reply to this.
You are comparing apples to oranges. These movies, specifically for X_Men, will be 2-3 years apart (or at best 9 months , if there are solo films). With comics, they were every month.
So with a 6 person team, theoretically you could have 2 issues a year that focus on each individual character, or at least have a year where it feels that EVERY character gets a decent amount of focus.
ALso, with movies, the stakes are much bigger, financially. And communication between fans is near instanaeous.
We also have recent history of movies. SUre, the 2000 X-men movie didn't need an intro. But then it felt like the focus wa smainly Wolverine , Professor X and Magneto. So "central" characters (at least form the past), like Cyclops were tossed to the side. When Cyclops was killed in Last Stand, people weren't emotionally sad when he died .... they were more more mad that he didn't get much time previously , for us to even care about his death.
the financial benefit for the studios is that, with the RIGHT introduction, you get people excited for the project that truly focuses on that character. In my theater, the crowd went wild when we heard Wonder Woman's theme , the crowd went wild (and the fact that it was the DCFU's lead film domestically shores that up). WHen T'Challa and Peter were introduced in Civil War, that certainly primed the pump for their movies, and they too are the leaders domesticaly for Marvel Movies (outside of Avengers).
Theoretically, they COULD use web snippets and other means in between to build up interest in characters. But it seems like an intro in another movie could be one of the best ways to get the hype going.