

It depends on a particular community.
Communities like nostupidquestions are not expected to have posts with important news or problems one might google a year later.
Tech-focused communities, on the contrary, are expected to keep posts forever, so that important information will be accessible. However, some people delete their posts after their problem is solved. This is highely discouraged.
And Lemmy ain’t just one site. Yeah.







One post is a couple of kilobytes, but there are hundreds of posts daily, you know. Also comments, also attachments. And no community exists in vacuum, they are parts of much larger instance servers. So this is among the least disruptive ways to save storage space.