An on-call engineer writes a post-incident summary at 3am: what broke, the four commands that diagnosed it, a table of affected regions, and the follow-ups. On Pastebin that arrives as one column of monospace text in which the table is not a table, the headings are not headings, and the four commands are visually identical to the prose around them — so the manager reading it on a phone at 7am scrolls, gives up, and asks for a summary of the summary.
The same text pasted here as Markdown renders as a document: the headings are navigable, the table is a grid, the commands sit in a code block that can be copied in one tap. Two hours later someone spots that a region was listed wrong — the engineer edits the page and the URL already in the incident channel now shows the correction, rather than a second link that half the thread will never see. What Pastebin still does better: if all you need is to dump 400 lines of raw log for a colleague to grep, its paste box is faster and nobody needs the output to be pretty.