Explanation
The practical significance is scheduling. Anything reactive goes stale before it publishes if it was made two weeks in advance, so an account that wants a buffer has to make most of its content evergreen. That is a content-strategy consequence of a logistics decision, and it is usually discovered the other way round.
Evergreen material also keeps accumulating views long after posting, particularly on YouTube Shorts and increasingly on TikTok search. A video that gets a steady trickle for a year can out-total one that spiked and died.
The common mistake
Confusing evergreen with timeless in tone. Evergreen content can be specific, opinionated and current in reference; what it cannot be is dependent on something the viewer needs to have seen this week.