Besides marketability, film is a visual medium, and you want to be looking at the actor, not at the bottom of the screen.

Consider Better Call Saul, and >!Nacho's death scene. Logically, all the characters there should be speaking Spanish, but you want to focus on the rage on Nacho's face as he curses Hector. Plus, not all the actors in the scene speak great Spanish, so better to keep it in English.!<