The article gives a simple reason: some things support it. If you want nice snippets in google search, Instagram, zotero etc.. you can use it.

The real reason was always "so you can publish data people can use programmatically" but turns out this doesn't work cause the interest of publishers ("visit my site") and the interest of consumers ("I want an answer") are not aligned.

It seemed people in the 2000s had some sort of mystical belief about computers that if you took all your data and put it in some kind of XML format it would give you good karma.