If you do not have any audio outputs (including in-built speakers) enabled/connected to your computer, subtitles do not show up in-game.

Link to video showing lack of subtitles: https://drive.google.com/file/d/1z9rcG-C44MaYSjNbnI9FV19nu6Wi1HnQ/view?usp=sharing
Attached screenshot shows the audio devices I disconnected for the video.