Doing so might have spoiled one of the plot’s big reveals.
One of the least surprising, though still enjoyable, cameos in Captain Marvel was the brief, punchy appearance of Ronan the Accuser. Ronan doesn’t do much, but his appearance as the premiere Accuser of the Kree Empire established a sense of continuity with Guardians of the Galaxy and makes the cosmic side of the MCU feel consistent. Also, he’s just a pleasant guy. Nice shade of blue.
As shared in the Director’s Commentary for Captain Marvel, the directors purposefully limited the scope of his appearance and decided not to introduce him until late in the film for one simple reason: introducing him early might have given away the movie’s big twist for comic fans.
See, in the film, the Kree are, well, they’re the baddies. Here’s the relevant quotes, as transcribed by CinemaBlend:
Anna Boden: Here we have the Accuser ships that are the kind of bomb squad of the Kree. So we’ve already met Starforce which is like their SEAL Team Six and now we see the bomb squad that’s going to be bombing a Skrull stronghold in the South. We played a lot with the question of when we introduce Ronan in this movie. Should we introduce him at the beginning of the film as the head Accuser of these Accuser ships or do we hold onto that reveal until later?
Ryan Fleck: Yeah, I think it was more effective to hold on because it was giving it away too soon that the Kree were the bad guys because everyone associates them with Guardians of the Galaxy and it really just gave away too much too soon.
Boden and Fleck were worried, rightly, I think, that casual viewers would get the quick hint that Ronan = Villain and put together that the Kree Empire was not a heroic one. Though, really, are there heroic empires?
Captain Marvel is out on Blu-Ray now.