Infinite scroll

Items load continuously as you move, so there is no end of page and no moment where a viewer decides whether to carry on. Every short-form feed works this way, and it sets what an opening has to survive: your competition is the swipe, available at any frame, at no cost to the viewer.

It also explains why watch-through on a Short behaves so differently from retention on a long video. Someone who clicked a ten-minute video has already committed something. Someone in the feed has committed nothing and reverses out the moment attention dips.