Wedge Antilles, the starfighter pilot for the Rebel Alliance in the original Star Wars trilogy, didn't appear in Rogue One: A Star Wars Story, and there are specific reasons why.
Despite both Red and Gold Leader showing up in the film during the Battle of Scarif, Wedge didn't appear. On Twitter, Lucasfilm Story Group's Pablo Hidalgo explained on Twitter that Wedge wouldn't actually be in the battle, as he had never seen the Death Star before A New Hope. In the film, Wedge says, "Look at the size of that thing!" when he first sees the Death Star in A New Hope, and Lucasfilm and Hidalgo didn't want to ruin the meaning of that line.
Another major reason for Wedge's absence is because there wasn't enough footage of him that Lucasfilm could use. On the other hand, Red and Gold Leader had tons of unused footage from the original trilogy that Rogue One director Gareth Edwards decided to use, but Skywalker Sound's Matthew Wood revealed that Wedge can still be heard (with David Ankrum providing the voice for the character) in Rogue One guiding the Rebel Pilots to their starships.