What’s up with attachments linking to other attachments?

What’s up with attachments linking to other attachments?

Something I’ve recently noticed in all of the Twenty * bundled themes is that media on the attachment pages are auto-linked to the next media in the gallery. What’s the point of having Next/Previous pagination links if you’re going to link the media anyway? I’d venture to say that if the media links to anything, it should be to its source.