I suppose it does function as an engagement hack, but I like ephemeral messaging like this because it is low-stakes and I often don't care strongly whether any individual sees my post or not. If I did care, I'd simply send them a message directly! So at least in this sense, the short timeframe is a feature that defines the medium for me.

Of course, you could allow customization of the time interval, but that adds another layer of complexity, and other platforms that use stories have already pretty much standardized on a timeframe of 24h, so it's easier for platform newcomers to understand.