A thought as a fellow 19-year-old male: I feel like this format leads to a lower quality understanding of the text as opposed to reading it, a factor to the prevalence of text over footage is the interestingness of the text itself, combined with the footage for background. It makes it much easier to just tune out the whole thing and not pay attention. I personally haven't ever used tiktok so I'm not familiar with the nature of the platform, but I could see this format being useful as an entry, but less useful for actual comprehension of the topics contained.
However this may just be my lack of experience with audiobooks talking, I have a friend who almost exclusively listens to books, he explained to me that you get a lot better the more you read(?) that way, so it could just be that.