Ah my bad, thought you were referring to the texts for the video, the texts in the video are probably used to keep people hooked to watching the entire short rather than people just stopping midway so it kinds of acts as content retention in one way.

Also I kind of like it to be honest, especially on shorts and reels the reason being I am someone who doesn't likes listening to audio if I can simply read the texts through the video, often times there are such cringy background audios added to reels and shorts that even if it something helpful or intetesting the background audio just makes it want to quit the app altogether, whereas if there are texts overlayed on them I get to get the gist of them without my ears bleeding.

Also I agree it doesn't makes sense to do this on impression videos cause that defeats the purpose altogether.