Explanation
The value is that durations become explicit rather than implied. A script reads at whatever speed you read it; a shot list states that the setup takes six seconds, which is the information that makes the problem obvious.
It also doubles as a brief. The same list works as an instruction to a freelancer or as a generation prompt, which is what makes it worth writing even for projects where nothing is being outsourced.
The common mistake
Making it visual. The value is in the sequence and the durations, so a text list is not a lesser version of a drawn storyboard, it is the part that does the work.