Way back when YouTube videos were limited to 15 minutes, even then the repeated advice of posting shorter videos, where 3½ minutes was determined the magic sweet length for maximum viewership, I was inconvenienced at the 15-minutes length limitation because at the time I wanted to post videos that stretched to 20 or sometimes 30 minutes.
 I arrived at the thought that it is not the YouTube algorithms feeding that suggestion nor necessarily audience short attention span but the harsh reality that most moments in people's lives can fit within a 3½ minutes time frame.

     Talking head vlogs, recorded performances, including discussion panels, and TV show or movie recap podcasts excluded, videos that center around travel or life events are more fluff than substance. Take for example a graduation video, for the family and friends who are trying to capture that special moment when their person of interest walks across the stage is far less than the hours of footage recorded of all the other nonamed person also graduating and walking across that same stage.
 Along the same lines, travel videos contain mostly B roll footage covering the transitory scenes, how long is a shot of some one entering their hotel room, not much, likewise scenes of skiing down a slope, or sliding down a tubed waterslide at a theme park. The most (interesting) and actionable moments recorded are brief, like life according to Hobbes.

 Case in point, here is a video used as a demo for Final Cut Pro, found on the latest MacBook Pro at an Apple store. The video was professionally done, hours of film footage, and several takes to get the scene right. All edited down to a final finished product of 1 minute and 12 seconds. Here was content wherrein the people were doing something.