Why not fight in ANH then? He could’ve got to the plans before Leia sent then away with R2. I normally wouldn’t nitpick the point because obviously a fight like that wouldn’t have worked in 1977, but so many people are claiming that R1 is a fluid lead-in to the OT that it’s worth mentioning. As for the dogfight, he’s the best starpilot in the galaxy and the Death Star was about to be blown up just before it could destroy the rebellion.

EDIT: It was just an excuse to get a Vader lightsaber scene in the movie.