Because it's an enormous flood of content that overwhelms trying to browse All otherwise, especially by New. Or at least that was the case a couple years ago, maybe it's changed now that the community has split up into 3 parts.

It was particularly a concern back before Lemmy had implemented the Scaled sort function and changed how Hot worked. Perhaps PieFed, back upon tinkering with its own sort functions, similarly tried to make that process easier to see content other than from 196 and memes?