When I drag and drop a JPG/PNG/PDF/AI file from Finder into an Illustrator document, it normally drops in as a link. However, sometimes it unexpectedly embeds the artwork instead of linking it. If I try again repeatedly, it continues to embed, so to fix it I have to go to File > Place and ensure that "Link" is selected (which it already is). After that, if I drag-and-drop from Finder again, it links the artwork as expected.

This issue is seemingly random and I can't figure out exactly how to reproduce it. I always link files (not embed them) when I place them via File > Place or via drag-and-drop, so I don't know why it sometimes decides to embed.